chore: consolidate configuration in google-cloud-pom-parent and google-cloud-jar-parent

[meltsufin]

• Attempts to centralize all dependency version management in the root pom.xml and the new google-cloud-jar-parent.
• Introduces the consolidate_config.sh script to help apply the change across all modules
• Reduces the scope of renovate bot to just the parent poms
• There are still many locations where versions are declared outside of the root pom and are not managed by release-please. That will be addressed in the follow-up PRs. For now, this PR adds a CI check to find such violations.

Fixes: #8543
Fixes: #8530
Fixes: #8522
Fixes: #8548

[suztomo]

If the root pom.xml has dependencyManagement section, ensure the small BOMs do not inherit the root pom.xml
E.g.,
https://github.com/googleapis/google-cloud-java/blob/main/java-accessapproval/google-cloud-accessapproval-bom/pom.xml#L10

(I remember you have a pull request that fixes it. Where is it now?)

[meltsufin]

@suztomo The script is set_parent_pom.sh, but it looks like it has a bug.

[meltsufin]

@suztomo Do we need a parent at all for the boms?

[suztomo]

The parent is for release plugins.

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[suztomo]

In this pull request, can you add few paragraphs in README.md (or somewhere) that explain why we introduce google-cloud-pom-parent and google-cloud-jar-parent, and their roles (What kinds of elements should they have)? The paragraphs should cover the things you verbally explained yesterday and the maintainers 1 year later will immediately understand the design.

[suztomo]

I think google-cloud-gapic-bom, google-cloud-pom-parent, and google-cloud-jar-parent all should have the same value but currently it's maintained by different key such as {x-version-update:google-cloud-jar-parent:current}. Can you set them with 1 key?

[meltsufin]

I think google-cloud-gapic-bom, google-cloud-pom-parent, and google-cloud-jar-parent all should have the same value but currently it's maintained by different key such as {x-version-update:google-cloud-jar-parent:current}. Can you set them with 1 key?

True, but for now I like to keep the convention of the annotation matching the artifactId. I now have scripts that rely on this.

[meltsufin]

In this pull request, can you add few paragraphs in README.md (or somewhere) that explain why we introduce google-cloud-pom-parent and google-cloud-jar-parent, and their roles (What kinds of elements should they have)? The paragraphs should cover the things you verbally explained yesterday and the maintainers 1 year later will immediately understand the design.

Added repository structure documentation: 512f907.