Revert pr #16050

[andsel]

Release notes

Bugfix a regression which resulted in missed environment variables resolution inside pipelines.yml

What does this PR do?

Revert pr #16050, which avoided to replace environment variables (${VAR}) inside config.string in the pipelines.yml file, but that created a regression, because env vars is expected to be replaced in all the other yaml keys.

Why is it important/What is the impact to the user?

Environment variables has to be resolved in config/pipelines.yml. With previous PR #16050 was tried to fix a problem linked also to resolution, which generated errors (and prohibited LS to start) if env vars were referred in commented code inside config.string definition in pipelines.yml. The fix was to avoid resolution at all in pipelines.yml but that generated a regression, hence this revert PR.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files (and/or docker env variables)
• I have added tests that prove my fix is effective or that my feature works

Author's Checklist

• [ ]

How to test this PR locally

Related issues

• Relates 8.14.0 environment variables stopped working #16199
• Relates Commented out variable substitutions may still be evaluated in pipelines.yml #16008
• Relates Fix the exception behavior when config.string contains ${VAR} in the comments. #16050

Use cases

Screenshots

Logs

[elastic-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarQube

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: 130ddac

cc @andsel

[yaauie]

I'm +1 to merging this revert on main and back-porting to 8.14, then following up to re-address the other issue separately.

[jsvd]

LGTM

[jsvd]

@logstashmachine backport 8.14