fix(source-intercom): conversation parts stream moved to per-partiition state

[lazebnyi]

What

Conversation parts stream has nested global state format what follow to skipping parent records if it has cursor value less that state. But as conversation can update independant of each others we can update state before child record will be submited and returned in the response.

How

Update state to per-partition format to avoid skiping parents records.

Review guide

1. manifest.yaml

User Impact

This is can affect on the speed of sync as we will sync parent in full refresh mode.

Can this PR be safely reverted and rolled back?

• [x] YES 💚 (with condition if we will migrate state to original format)
• [ ] NO ❌