Remove high quality mode from codebase

[sakertooth]

Many, many years ago (93a456c), high quality mode was merely disabled after it was noted that it can be problematic (which in fact it is) rather than being completely removed. Remove it from the codebase so we can get rid of some code and clean things up a bit.

This feature (and qualitySettings as a whole actually) is problematic since the settings are not applied for all of our resampling states, and the code currently only applies it for the resampling state in the current audio device (which is only utilized when we are moving from one sample rate to another and does not apply for AFP and sample tracks for example, so essentially the effect of higher quality interpolation is not even observed).

There are other reasons as well (having to reopen a new entire audio stream each time the quality changes, which does not seem like a good workflow, as well as the fact the oversampling multiplier is applied twice, since the sample rate of the audio device is set to AudioEngine::processingSampleRate, which is the original rate with the multiplier applied, so calls to AudioEngine::processingSampleRate would get a sample rate of deviceSampleRate * multiplier * multiplier).

Since its disabled for the most part, its mostly just in the way at this point (regardless of all the problems it would bring if it was implemented in full effect), so there's no need for it to be in the codebase.