fix: meter WAC compute per segment, not the whole sleep (#10985)

* fix: clear started_at when a WAC parent suspends

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AzS5d5Dc3GL49kWZPQAQCg

* fix: restore started_at on the WAC dispatch rollback, fail loudly on a no-op suspend

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AzS5d5Dc3GL49kWZPQAQCg

* fix: restore the pulled segment start on the WAC dispatch rollback

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AzS5d5Dc3GL49kWZPQAQCg

* feat: meter WAC execution per segment instead of only the last one

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AzS5d5Dc3GL49kWZPQAQCg

* fix: make the cloud feature self-sufficient per crate

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AzS5d5Dc3GL49kWZPQAQCg

* chore: name windmill-common/cloud directly in the worker cloud feature

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AzS5d5Dc3GL49kWZPQAQCg

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Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>