add: ETCM-9734 caching for governed map data

[jankun4]

Description

link
Adds Cached GovernedMap DataSource implementation, and uses it in demo-node

Checklist

• Commit sequence broadly makes sense and commits have useful messages.
• The size limit of 400 LOC isn't needlessly exceeded
• The PR refers to a JIRA ticket (if one exists)
• New tests are added if needed and existing tests are updated.
• New code is documented and existing documentation is updated.
• Relevant logging and metrics added
• Any changes are noted in the changelog.md for affected crate
• Self-reviewed the diff

[AmbientTea]

See my comment on the cache safety. I think we're missing some checks. My suggestion is to avoid the issue completely and just replace the cache on every miss, this is what we're doing with native tokens and I don't see a scenario where having more complex cache extension logic makes has any substantial benefits.

The cache is completly replaced every time now.