[FLINK-35654][docs] Add CDC release verification & Installation guide

[yuxiqian]

This closes FLINK-35654.

Currently, ASF voting process requires vast quality verification before releasing any new versions, including:

• Tarball checksum verification
• Compile from source code
• Run pipeline E2e tests
• Run migration tests
• Check if jar was packaged with correct JDK version
• ...

Adding verification SOP in "Contribution guide" of Flink CDC docs should help developers verify future releases more easily.

[yuxiqian]

Thanks for @morazow's comments! Addressed most of them, and left some that requires further discussion.

[github-actions[bot]]

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[github-actions[bot]]

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