Added missing test case for migrations when using sql structure
Remove unused require

We're not longer using `ipaddr` in schema dumper
remove unnused method from test
Merge pull request #15655 from fabianrbz/remove-unused-method-in-test

remove unnused method from test
Merge pull request #15647 from sgrif/sg-unused-require

Remove unused require
Removed warning actionpack url.rb

Before:

/Users/Juan/dev/rails/actionpack/lib/action_dispatch/http/url.rb:95: warning: shadowing outer local variable - port

After:

No warning
Merge pull request #15662 from JuanitoFatas/patch/remove-warning

Removed variable shawdowing warning in actionpack url.rb
Add unregister_template_handler to prevent leaks.
Fixed automatic maintaining test schema to properly handle sql structure schema format.

Additionally:
* It changes `purge` task on `sqlite3` adapter to recreate database file, to
be consistent with other adapters.
* Adds `purge` step when loading from `schema.rb`
Merge pull request #15590 from zuhao/refactor_actionview_register_template_handler

Add unregister_template_handler to prevent leaks.

Conflicts:
	actionview/CHANGELOG.md
Merge pull request #15394 from morgoth/fix-automatic-maintaining-test-schema-for-sql-format

ActiveRecord::Migration.maintain_test_schema! doesn't work with structure.sql

Conflicts:
	activerecord/CHANGELOG.md