Deprecate ZetaSQL

[Abacn]

First step of #34423

• Announce deprecation in Beam website, changes, Javadoc

• Issue warning on SqlTransform expansion to ZetaSQL

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[Abacn]

PreCommit SQL currently failing on master branch: https://github.com/apache/beam/actions/runs/14348271230 not related to this change