Integ 3042/pydantic upgrade

[ceciliastevens]

• Upgrades pydantic compatibility to the newest version
• Fixes a bug where the watchlist v2 methods were still using watchlist v1 data structures
• Adds support for the new session state CLOSED_TP_BENIGN
• Adds support for the ON filter in file event searches
• Removes some old guides that referenced outdated methods

[ceciliastevens]

Some of the work on the backend that we're depending on for these changes is not yet finalized. Putting this in draft for now until we know for sure what changes will be made.

Edit 2026-01-12 - finalized list of states is now confirmed, no changes here are necessary, this PR is ready as-is.

[johnsonjben]

I see we now have like a "watchlist v2 response", we aren't changing anything about the current response, correct?

[ceciliastevens]

I see we now have like a "watchlist v2 response", we aren't changing anything about the current response, correct?

The V2 method uses the V2 response object, the deprecated V1 method continues to use the old response object, which has not changed.