release-24.1: workload/schemachanger: apply statement_timeout out to CTAS

[fqazi]

Backport 1/1 commits from #148761 on behalf of @fqazi.

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Previously, the schema changer workload never used statement_timeouts since schema changes are normally not predictable operations. However, since we added CREATE TABLE AS support, its possible to have multiple joins where a CREATE TABLE AS can take more then 5 minutes. This patch modifies the operation generator support adding statement timeouts for individual statements.

Fixes: #148342

Release note: None

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Release justification: test only change

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

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[cockroach-teamcity]

This change is