release-23.2.5-rc: changefeedccl: disable drain watcher by default

[blathers-crl]

Backport 1/1 commits from #123370 on behalf of @wenyihu6.

/cc @cockroachdb/release

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#102717 introduced a mechanism allowing for an orderly shutdown of changefeed
aggregators and an up-to-date frontier information to reduce duplicates during
a node restart in 23.2. However, we've recently identified a bug that could
lead to unexpected behavior. It's unclear where the bug is yet. This patch disables
this feature by default.

Fixes: #123371
Release note: Disabled a changefeed optimization on reducing duplicates during
aggregator restarts due to its bad performance.

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Release justification: Low risk bug fix to disable a changefeed optimization on reducing duplicates during
aggregator restarts due to its unexpected behavior.

[blathers-crl]

Thanks for opening a backport.

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[cockroach-teamcity]

This change is