extendable param files add a warning when referencing to a non-existent .bicepparam file

[polatengin]

Bubbling up the diagnostics error when the referenced file does not exist in the extends statement

// main.bicepparam file exists
// VALID
using none
extends './main.bicepparam'

// even if the main.json file exists this fails, because extends keyword only accepts .bicepparam files
// throws BCP 404
// INVALID
using none
extends 'main.json'

// non-exist-main.bicepparam file doesn't exist
// throws BCP 091
// INVALID
using none
extends 'non-exist-main.bicepparam'

Fixes #14847

[github-actions]

Test this change out locally with the following install scripts (Action run 11411223490)

VSCode

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-vsix.sh) --run-id 11411223490

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-vsix.ps1) } -RunId 11411223490"

Azure CLI

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-cli.sh) --run-id 11411223490

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-cli.ps1) } -RunId 11411223490"

[github-actions]

Dotnet Test Results

    72 files   -     35      72 suites   - 35   30m 21s ⏱️ - 11m 33s
11 360 tests  -     22  11 359 ✅  -     23  0 💤 ±0  1 ❌ +1 
26 451 runs   - 13 212  26 450 ✅  - 13 213  0 💤 ±0  1 ❌ +1 

For more details on these failures, see this check.

Results for commit 7a5fb72. ± Comparison against base commit b09ba5e.

♻️ This comment has been updated with latest results.