Squash migrations through v3.6

[jeremystretch]

Proposed Changes

Squash all existing migrations up to the v3.6.0 release. (This is a repeat of what we did for the v3.0 release under #6471.)

Justification

Squashing migrations optimizes necessary changes to the database schema and reduces installation time.

[jeremystretch]

Re-opening this as there's an issue with the way squashed migrations are split:

django.db.migrations.exceptions.InconsistentMigrationHistory: Migration circuits.0004_squashed is
applied before its dependency circuits.0003_squashed on database 'default'.