DEV: Use filesystem-based SchemaCache in development (PR #12901)

In development we regularly restart/reload Rails, which wipes out the schema cache. This then has to be regenerated using DDL queries on the database.

Instead, we can make use of the rake db:schema:cache:dump command. This will dump the schema cache to a YAML file, and then load it when needed. This is significantly faster than rebuilding the cache from DDL queries every time.

See also #12900