Allow default_metric deprecation warning in TSDB ESQL YAML tests

[MattAlp]

Summary

• Allow the default_metric deprecation warning in the affected esql/40_tsdb YAML REST test sections.
• Apply the warning allowance to both to_aggregate_metric_double with multi_values and TS Command grouping on text field so warnings do not fail otherwise-correct assertions.

Closes: #142964

[elasticsearchmachine]

Pinging @elastic/es-analytical-engine (Team:Analytics)

[limotova]

Going to defer to @gmarouli on this but I think we want to investigate why this is happening a bit more before muting the warnings entirely (see #143217)

[gmarouli]

Thanks @limotova , I agree, I am not sure if this is the right fix. And I cannot reproduce it to verify this.
I have to admit that I expected this warning to be thrown when editing or accessing the mapping and not during an ES|QL query. I have seen other similar failures and I am adding extra logging to be able to debug it further, see #143217, I have unmuted this test there.

If you agree, I think we should wait to collect more data, before deciding if we should proceed with this change.

[MattAlp]

Ok, let's put this PR on hold in favor of seeing why this warning surfaces

[gmarouli]

Theoretically, the root cause of this is fixed by #144040. I will close this PR and monitor the failures.