Pass the request ctx rather than use the globals in the app

[pgjones]

The globals have a performance penalty which can be justified for the convinience in user code. In the app however the ctx can easily be passed through the method calls thereby reducing the performance penalty.

This may affect extensions if they have subclassed the app and overridden these methods.

Checklist:

• [x] Add tests that demonstrate the correct behavior of the change. Tests should fail without the change.
• [x] Add or update relevant docs, in the docs folder and in code.
• [x] Add an entry in CHANGES.rst summarizing the change and linking to the issue.
• [x] Add .. versionchanged:: entries in any relevant code docs.
• [x] Run pre-commit hooks and fix any issues.
• [x] Run pytest and tox, no tests failed.