TSVB wrong default date field on default index-pattern

[alexwizp]

Fix: #36264

Summary

When creating a fresh TSVB visualization, the default index pattern is used.
The first data query is then issued with that default index-pattern against what should be the default date field. I said "should be" because if I'm not currently seeing this behaviour if I'm using the kibana_sample_data_ecommerce that has the order_date as default date field instead of the standard @timestamp.

Checklist

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[elasticmachine]

Pinging @elastic/kibana-app

[elasticmachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request

[sulemanof]

LGTM
I would also set the default time interval as a placeholder

[alexwizp]

@sulemanof default value for time interval is not related to these changes but it was already fixed in the following PR #36081

[markov00]

Code LGTM. Tested locally changing default index patterns and using different override index patterns.