Setup blazer on admin to query data

[jenshenny]

This PR adds blazer to the admin to better query data. This would make it easier verify assumptions in the data (eg. removing unconfirmed users #6088).

To access: go to /admin/blazer

Flows to poke around:

• Create a new query (and view data from blazer tables)
• Create a new dashboard
• Create a check

New tables (generated by bin/rails generate blazer:install)

blazer_queries: saved queries
blazer_audits: record of queries that have been run
blazer_dashboards: can create a dashboard that would show different queries
blazer_dashboard_queries: join table for queries and dashboards
blazer_checks: Can create checks to check invalid data and would notify on a recurring basis (is not setup)

Follow ups

• Queries are wrapped in a transaction, but should create a readonly user https://github.com/ankane/blazer?tab=readme-ov-file#postgresql (I want to test this on staging first before doing this).
• Creating a dashboard has a n+1 query, will propose a fix upstream

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.24%. Comparing base (8fa3e3d) to head (b2c75c1).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6091   +/-   ##
=======================================
  Coverage   97.24%   97.24%           
=======================================
  Files         476      476           
  Lines        9785     9785           
=======================================
  Hits         9515     9515           
  Misses        270      270           

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