feat(web-analytics): Add option behind FF to switch to V2 web analytics

[robbie-c]

Note: this will invalidated the query cache, so my plan is to merge this outside of peak times, e.g. at the start of the work day tomorrow

Problem

We don't have a way of switching people to the v2 table. It's backfilled for team 2 and I want to start dogfooding :)

Changes

Add a setting behind a FF to change the sessions table version

Does this work well for both Cloud and self-hosted?

Yes

How did you test this code?

Changed the setting locally, checked that the clickhouse that was actually run matched the expected version

[github-actions[bot]]

Size Change: +224 B (+0.02%)

Total Size: 1.06 MB

ℹ️ View Unchanged

| Filename | Size | Change | | :--- | :---: | :---: | | `frontend/dist/toolbar.js` | 1.06 MB | +224 B (+0.02%) |

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