ci(dra): support qualifier for the main branch

[v1v]

Motivation/summary

conduct a staging DRA upload from the main branch (we would usually use the 9.0 branch but will make an exception here) using “alpha1” as the qualifier.

Implementation details

• The ELASTIC_QUALIFIER environment variable should be set when building/packaging the APM Server or using the BK DRA job if a qualifier needs to be used.

• Use LDFLAGS to honour the ELASTIC_QUALIFIER value.
• Replace version.Version references with version.VersionWithQualifier().

Checklist

• Update CHANGELOG.asciidoc
• Documentation has been updated

For functional changes, consider:

• Is it observable through the addition of either logging or metrics?
• Is its use being published in telemetry to enable product improvement?
• Have system tests been added to avoid regression?

How to test these changes

After merging it. However, a dry-run will happen in a feature branch but using the list commands instead of collect.

$ ELASTIC_QUALIFIER=alpha1 make package-snapshot
$ ELASTIC_QUALIFIER=alpha1 make apm-server
$ ./apm-server version
$ ls -ltra build/distributions

And also without ELASTIC_QUALIFIER=alpha1

$ make package-snapshot
$ make apm-server
$ ./apm-server version
$ ls -ltra build/distributions

For instance, I removed the docker generations and test package-snapshot:

 ls -ltra build/distributions 
total 407752
-rw-r--r--   1 vmartinez  staff  26128584 Jan 15 18:32 apm-server-9.0.0-alpha1-SNAPSHOT-darwin-x86_64.tar.gz
-rw-r--r--   1 vmartinez  staff  25964854 Jan 15 18:32 apm-server-9.0.0-alpha1-SNAPSHOT-linux-x86_64.tar.gz
-rw-r--r--   1 vmartinez  staff  24325940 Jan 15 18:32 apm-server-9.0.0-alpha1-SNAPSHOT-linux-arm64.tar.gz
-rw-r--r--   1 vmartinez  staff  26266940 Jan 15 18:33 apm-server-9.0.0-alpha1-SNAPSHOT-windows-x86_64.zip
-rw-r--r--   1 vmartinez  staff  26460610 Jan 15 18:33 apm-server-9.0.0-alpha1-SNAPSHOT-amd64.deb
-rw-r--r--   1 vmartinez  staff  24911010 Jan 15 18:33 apm-server-9.0.0-alpha1-SNAPSHOT-arm64.deb
-rw-r--r--   1 vmartinez  staff  27335740 Jan 15 18:33 apm-server-9.0.0-alpha1-SNAPSHOT-x86_64.rpm
drwxr-xr-x  10 vmartinez  staff       320 Jan 15 18:33 .
-rw-r--r--   1 vmartinez  staff  25626665 Jan 15 18:33 apm-server-9.0.0-alpha1-SNAPSHOT-aarch64.rpm
drwxr-xr-x  20 vmartinez  staff       640 Jan 15 18:34 ..

DRA

With a qualifier sets to alpha1, see this build
Without a qualifier, see this build

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