[Bug] Fix issues related to secondary EIPs and Private IPs being updated

[drewtul]

Description

Currently updating the EIP associations for a NAT Gateway causes a replacement, which is not required.

This removes ForceNew from secondary_private_ip_address_count and fixes issues allowing EIPs to be updated without recreating the resource which affects network connectivity for the duration.

Also makes it possible to move from secondary_private_ip_address_count being specified to specifying exact IPs in secondary_private_ip_addresses allowing users to increase from their initial number of private ips for a private NAT gateway.

Relations

Closes #33964.
Closes #34268.
Closes #36360.

References

Output from Acceptance Testing

%  make testacc ACCTEST_PARALLELISM=3 TESTS=TestAccVPCNATGateway_ PKG=ec2
make: Verifying source code with gofmt...
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go1.23.5 test ./internal/service/ec2/... -v -count 1 -parallel 3 -run='TestAccVPCNATGateway_'  -timeout 360m -vet=off
2025/02/17 12:57:40 Initializing Terraform AWS Provider...
=== RUN   TestAccVPCNATGateway_basic
=== PAUSE TestAccVPCNATGateway_basic
=== RUN   TestAccVPCNATGateway_disappears
=== PAUSE TestAccVPCNATGateway_disappears
=== RUN   TestAccVPCNATGateway_ConnectivityType_private
=== PAUSE TestAccVPCNATGateway_ConnectivityType_private
=== RUN   TestAccVPCNATGateway_privateIP
=== PAUSE TestAccVPCNATGateway_privateIP
=== RUN   TestAccVPCNATGateway_tags
=== PAUSE TestAccVPCNATGateway_tags
=== RUN   TestAccVPCNATGateway_secondaryAllocationIDs
=== PAUSE TestAccVPCNATGateway_secondaryAllocationIDs
=== RUN   TestAccVPCNATGateway_secondaryPrivateIPAddressCount
=== PAUSE TestAccVPCNATGateway_secondaryPrivateIPAddressCount
=== RUN   TestAccVPCNATGateway_secondaryPrivateIPAddressCountToSpecific
=== PAUSE TestAccVPCNATGateway_secondaryPrivateIPAddressCountToSpecific
=== RUN   TestAccVPCNATGateway_secondaryPrivateIPAddresses
=== PAUSE TestAccVPCNATGateway_secondaryPrivateIPAddresses
=== RUN   TestAccVPCNATGateway_SecondaryPrivateIPAddresses_private
=== PAUSE TestAccVPCNATGateway_SecondaryPrivateIPAddresses_private
=== CONT  TestAccVPCNATGateway_basic
=== CONT  TestAccVPCNATGateway_secondaryAllocationIDs
=== CONT  TestAccVPCNATGateway_SecondaryPrivateIPAddresses_private
--- PASS: TestAccVPCNATGateway_basic (174.04s)
=== CONT  TestAccVPCNATGateway_secondaryPrivateIPAddresses
--- PASS: TestAccVPCNATGateway_SecondaryPrivateIPAddresses_private (568.75s)
=== CONT  TestAccVPCNATGateway_secondaryPrivateIPAddressCountToSpecific
--- PASS: TestAccVPCNATGateway_secondaryAllocationIDs (591.50s)
=== CONT  TestAccVPCNATGateway_secondaryPrivateIPAddressCount
--- PASS: TestAccVPCNATGateway_secondaryPrivateIPAddresses (572.73s)
=== CONT  TestAccVPCNATGateway_privateIP
--- PASS: TestAccVPCNATGateway_secondaryPrivateIPAddressCount (171.92s)
=== CONT  TestAccVPCNATGateway_tags
--- PASS: TestAccVPCNATGateway_privateIP (203.95s)
=== CONT  TestAccVPCNATGateway_ConnectivityType_private
--- PASS: TestAccVPCNATGateway_tags (202.74s)
=== CONT  TestAccVPCNATGateway_disappears
--- PASS: TestAccVPCNATGateway_secondaryPrivateIPAddressCountToSpecific (564.72s)
--- PASS: TestAccVPCNATGateway_ConnectivityType_private (193.75s)
--- PASS: TestAccVPCNATGateway_disappears (220.74s)
PASS
ok      github.com/hashicorp/terraform-provider-aws/internal/service/ec2        1191.618s

[github-actions]

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[ewbankkit]

LGTM 🚀.

% make testacc TESTARGS='-run=TestAccVPCNATGateway_' PKG=ec2 ACCTEST_PARALLELISM=3
make: Verifying source code with gofmt...
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go1.23.5 test ./internal/service/ec2/... -v -count 1 -parallel 3  -run=TestAccVPCNATGateway_ -timeout 360m -vet=off
2025/02/25 15:58:21 Initializing Terraform AWS Provider...
=== RUN   TestAccVPCNATGateway_basic
=== PAUSE TestAccVPCNATGateway_basic
=== RUN   TestAccVPCNATGateway_disappears
=== PAUSE TestAccVPCNATGateway_disappears
=== RUN   TestAccVPCNATGateway_ConnectivityType_private
=== PAUSE TestAccVPCNATGateway_ConnectivityType_private
=== RUN   TestAccVPCNATGateway_privateIP
=== PAUSE TestAccVPCNATGateway_privateIP
=== RUN   TestAccVPCNATGateway_tags
=== PAUSE TestAccVPCNATGateway_tags
=== RUN   TestAccVPCNATGateway_secondaryAllocationIDs
=== PAUSE TestAccVPCNATGateway_secondaryAllocationIDs
=== RUN   TestAccVPCNATGateway_secondaryPrivateIPAddressCount
=== PAUSE TestAccVPCNATGateway_secondaryPrivateIPAddressCount
=== RUN   TestAccVPCNATGateway_secondaryPrivateIPAddressCountToSpecific
=== PAUSE TestAccVPCNATGateway_secondaryPrivateIPAddressCountToSpecific
=== RUN   TestAccVPCNATGateway_secondaryPrivateIPAddresses
=== PAUSE TestAccVPCNATGateway_secondaryPrivateIPAddresses
=== RUN   TestAccVPCNATGateway_SecondaryPrivateIPAddresses_private
=== PAUSE TestAccVPCNATGateway_SecondaryPrivateIPAddresses_private
=== CONT  TestAccVPCNATGateway_basic
=== CONT  TestAccVPCNATGateway_secondaryAllocationIDs
=== CONT  TestAccVPCNATGateway_privateIP
--- PASS: TestAccVPCNATGateway_privateIP (156.82s)
=== CONT  TestAccVPCNATGateway_secondaryPrivateIPAddresses
--- PASS: TestAccVPCNATGateway_basic (186.53s)
=== CONT  TestAccVPCNATGateway_SecondaryPrivateIPAddresses_private
--- PASS: TestAccVPCNATGateway_secondaryAllocationIDs (602.29s)
=== CONT  TestAccVPCNATGateway_ConnectivityType_private
--- PASS: TestAccVPCNATGateway_secondaryPrivateIPAddresses (565.47s)
=== CONT  TestAccVPCNATGateway_tags
--- PASS: TestAccVPCNATGateway_SecondaryPrivateIPAddresses_private (581.84s)
=== CONT  TestAccVPCNATGateway_disappears
--- PASS: TestAccVPCNATGateway_ConnectivityType_private (176.49s)
=== CONT  TestAccVPCNATGateway_secondaryPrivateIPAddressCountToSpecific
--- PASS: TestAccVPCNATGateway_tags (190.78s)
=== CONT  TestAccVPCNATGateway_secondaryPrivateIPAddressCount
--- PASS: TestAccVPCNATGateway_disappears (155.46s)
--- PASS: TestAccVPCNATGateway_secondaryPrivateIPAddressCount (195.30s)
--- PASS: TestAccVPCNATGateway_secondaryPrivateIPAddressCountToSpecific (418.86s)
PASS
ok  	github.com/hashicorp/terraform-provider-aws/internal/service/ec2	1203.534s