[Release 16.0]: Online DDL: timeouts for all gRPC calls (#14182)

[shlomi-noach]

Backport of #14182 to release-16.0

Description

Following the same lines of how #14165 solves #14164, this PR ensures there's reasonable timeout s for any gRPC call made by the Online DDL service.

Related Issue(s)

• Bug Report: throttler: gRPC logs indicate attempts to contact a decomissioned IP address #14164
• Throttler: set timeouts on gRPC communication and on topo communication #14165

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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