fix(docs-infra): calculate list of Angular Docs versions based on VERSION

[josephperrott]

fix(docs-infra): calculate the list of Angular Docs versions based on VERSION, append --config=release to docs build and serve the script. Support displaying the right color of navigation for the deprecated state.
fix(docs-infra): add scrollbar to version picker
fix(docs-infra): set initial adev docs version to 18
fix(docs-infra): remove --config=release from scripts for local development, write unit tests
fix(docs-infra): update CI tests step
fix(docs-infra): remove rc from the list
fix(docs-infra): update unit test to check count of versions

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/angular/angular/blob/main/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• angular.io application / infrastructure changes
• Other... Please describe:

What is the current behavior?

Issue Number: N/A

What is the new behavior?

Does this PR introduce a breaking change?

• Yes
• No

Other information

[josephperrott]

This PR was merged into the repository by commit e3aa2b5.

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