Update 7.x branch with the latest changes in the main branch

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What

7.x branch is not up to date with all the changes in main, so the renaming of main in the APM agents, Opbeans and other projects required to apply some changes in this repository.

As a consequence the builds in the 7.x branch are unstable sometimes.

Action

Create a new branch from main, update versions that refer to the nightly basis matrix and remove commits from main that should not be backported

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git --no-pager log --oneline --graph --decorate --abbrev-commit 5.x...main
* 9a0456d (HEAD -> 5.x, upstream/5.x) fix typo
* 5740351 remove EOL versions 7.7 and 7.8
* c2cd8ab versions: wrong versions
* bb37a5f (origin/5.x) Revert "test: run APM Server managed (#1031)"
* 69c1558 ci: use release
* 4580d85 Required change from the revert I made
* 3839999 use 7.16 references
* f0b54fe ci: remove trigger for EC/ECK validations
* 71c2146 Revert "Adapt to breaking changes in 8.0 (#1312)"

So far I reverted:

• Adapt to breaking changes in 8.0 #1312
• test: run APM Server managed #1031

Changed:

• CI pipelines to use the release alias
• Change versions with the current supported versions.

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#1412 is also needed to be backported :)