Simple audio filters (#5230)

* Add IIR Filter and Butterworth design functions

Signed-off-by: Martmists <martmists@gmail.com>

* naming conventions and missing type hints

Signed-off-by: Martmists <martmists@gmail.com>

* Link wikipedia in IIRFilter

Signed-off-by: Martmists <martmists@gmail.com>

* Add doctests and None return types

Signed-off-by: Martmists <martmists@gmail.com>

* More doctests

Signed-off-by: Martmists <martmists@gmail.com>

* Requested changes

Signed-off-by: Martmists <martmists@gmail.com>

* run pre-commit

Signed-off-by: Martmists <martmists@gmail.com>

* Make mypy stop complaining about ints vs floats

Signed-off-by: Martmists <martmists@gmail.com>

* Use slower listcomp to make it more readable

Signed-off-by: Martmists <martmists@gmail.com>

* Make doctests happy

Signed-off-by: Martmists <martmists@gmail.com>

* Remove scipy

Signed-off-by: Martmists <martmists@gmail.com>

* Test coefficients from bw filters

Signed-off-by: Martmists <martmists@gmail.com>

* Protocol test

Co-authored-by: Christian Clauss <cclauss@me.com>

* Make requested change

Signed-off-by: Martmists <martmists@gmail.com>

* Types

Signed-off-by: Martmists <martmists@gmail.com>

* Apply suggestions from code review

* Apply suggestions from code review

* Update butterworth_filter.py

Co-authored-by: Christian Clauss <cclauss@me.com>