Docs: Fix Data Retention Application terminology and add missing config/cleanup details

[kiran1287]

What we need

Update the Data Retention Application doc page to fix outdated terminology and fill in missing details about the app.

Requirements

1. Replace "OpenMetadata" with "Collate" throughout (keep the Java class name as-is).
2. Explain that the app also removes orphaned/stale data (relationships, tags, test cases) left behind when a parent entity is deleted, not just routine event cleanup.
3. Add the missing config options: testCaseResultsRetentionPeriod (1440 days) and profileDataRetentionPeriod (1440 days).
4. Add the missing orphan-based cleanup targets: entity relationships/hierarchies, tag usages, test cases, and time-series rows.

Reference

• Verified against DataRetention.java and dataRetentionConfiguration.json at the current open-metadata/openmetadata-collate submodule pin