EmergencyReparentShard: support ignored file-based replicas

[timvaillancourt]

Description

NOTE: for this PR to move forward, EmergencyReparentShard must know which replicas are semi-sync-enabled - currently it does not

This PR changes the EmergencyReparentShard behaviour for shards with mixed GTID-based and file-based replication positions. The only example scenario I can think of being a Vitess cluster in an "import phase" from a file-based source

Today (v23 stable) a shard in this mixed state will hard-fail to reparent. On one hand that is very safe, and on another it is very dangerous - an unplanned problem with the PRIMARY will not be fixed, likely resulting in downtime

This PR changes the behaviour to ignore the file-based replica and move forward with the reparent if we can ensure the replica is not a semi-sync acker

Related Issue(s)

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