fix(bigtable): Allow micro seconds in filter in Bigtable emulator

[bhshkh]

Issue: Bigtable emulator does not allow microseconds precision in timestamp range filter. E.g. when below code is run against emulator:

// milliseconds an hours ago
long milliTimestamp = Instant.now().minus(1, ChronoUnit.HOURS).toEpochMilli() * 1000;
.....
long microTimestamp = milliTimestamp + 345;
ConditionalRowMutation conditionalRowMutation = ConditionalRowMutation.create(tableId, rowkey)
    .condition(FILTERS.chain().filter(FILTERS.timestamp().exact(microTimestamp)))
    .then(mutation);
boolean success = dataClient.checkAndMutateRow(conditionalRowMutation);

Throws error:

com.google.api.gax.rpc.InvalidArgumentException: io.grpc.StatusRuntimeException: INVALID_ARGUMENT: Error in field 'timestamp_range_filter'. Maximum precision allowed in filter is millisecond.
Got:
Start: 1707777251311345
End: 1707777251311346

The above code runs successfully when run against an actual Bigtable instance

Cause: Emulator has a validation to check whether timestamp is in milliseconds
Fix: Remove validation from emulator

Closes: #9149