Add full job lifecycle examples to custom OpenLineage jobs docs (#37414)

* Add full job lifecycle examples to custom OpenLineage jobs docs

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* Add note explaining why step 2 is optional

* Clarify the note about optional for step 2

* Clarify optional RUNNING event note

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* Highlight product capabilities in overview

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

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Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: heron--