changefeedccl: emit mvcc_timestamp for avro format

[rharding6373]

This PR adds support for the mvcc_timestamp option with the avro format. Before this change, changefeeds using avro would not fail if mvcc_timestamp was specified, but would ignore the option. Now avro supports the mvcc_timestamp by adding mvcc_timestamp to the schema and emitting the mvcc value with the row data.

Epic: none Fixes: #123078

Release note (enterprise change): Adds changefeed support for the mvcc_timestamp option with the avro format. If both options are specified, the avro schema includes an mvcc_timestamp metadata field and emits the row's mvcc timestamp with the row data.

[cockroach-teamcity]

This change is 

[rharding6373]

TFTR!

bors r=andyyang890

[craig[bot]]

Build succeeded:

• linux_amd64_fips_build
• lint
• docker_image_amd64
• local_roachtest_fips
• macos_arm64_build
• check_generated_code
• macos_amd64_build
• acceptance
• local_roachtest
• windows_build
• examples_orms
• linux_arm64_build
• linux_amd64_build
• unit_tests

[rharding6373]

blathers backport 24.2 24.1 23.2

[rharding6373]

blathers backport 24.1.8-rc

[blathers-crl[bot]]

Based on the specified backports for this PR, I applied new labels to the following linked issue(s). Please adjust the labels as needed to match the branches actually affected by the issue(s), including adding any known older branches.

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Issue #123078: branch-release-24.1.8-rc.

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