v14 backport: CI: increase overall test timeouts for all OnlineDDL tests

[shlomi-noach]

Manual backport of #12584

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Description

Due to recent GitHub CI runners slowness, we're seeing some tests time out after 20min of running. These tests normally run for 5-6 min on a local dev env, and 20min used to give good margins. Not anymore.

This PR increases all Online DDL related tests timeouts to 30min.

Related Issue(s)

Checklist

• "Backport to:" labels have been added if this change should be back-ported
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on the CI
• Documentation was added or is not required

Deployment Notes

[vitess-bot]

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