Fix encoding error with non-prettified encoded responses (#1168)

* Fix encoding error with non-prettified encoded responses

Removed `--format-option response.as` an promote `--response-as`: using
the format option would be misleading as it is now also used by non-prettified
responses.

* Encoding refactoring

* split --response-as into --response-mime and --response-charset
* add support for Content-Type charset for requests printed to terminal
* add support charset detection for requests printed to terminal without a Content-Type charset
* etc.

* `test_unicode.py` → `test_encoding.py`

* Drop sequence length check

* Clean-up tests

* [skip ci] Tweaks

* Use the compatible release clause for `charset_normalizer` requirement

Cf. https://www.python.org/dev/peps/pep-0440/#version-specifiers

* Clean-up

* Partially revert d52a4833e461e1b16b7961a112ea5c53e93cd643

* Changelog

* Tweak tests

* [skip ci] Better test name

* Cleanup tests and add request body charset detection

* More test suite cleanups

* Cleanup

* Fix code style in test

* Improve detect_encoding() docstring

* Uniformize pytest.mark.parametrize() calls

* [skip ci] Comment out TODOs (will be tackled in a specific PR)

Co-authored-by: Jakub Roztocil <jakub@roztocil.co>