MysqlCtl: implement missing ReadBinlogFilesTimestamps function

[shlomi-noach]

Description

As per #14506, calls to ReadBinlogFilesTimestamps failed with rpc error: code = Unimplemented desc = method ReadBinlogFilesTimestamps not implemented.

This affects users of mysqlctld, but was not detected in endtoend tests, which were not using the same.

The function is added and now tested.

A release-18.0 backport is needed, but also requires a backwards-compatibility fix to 17.0, because the function ReadBinlogFilesTimestamps is new to v18. A special PR for 18 release to follow.

Related Issue(s)

Checklist

• "Backport to:" labels have been added if this change should be back-ported
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on the CI
• Documentation was added or is not required

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[vitess-bot]

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