Seperate input and certain functions from mixer #6992
Description
What part of EdgeTX is the focus of this bug?
Transmitter firmware
Current Behavior
As indicated in #2256, there are code paths that are not correctly aligned with their domain. In addition to that, some tasks, such as the mixer, are doing more than they should, thus blocking other tasks/capabilties when the mixer is not running. Take #53 for example. There is the symptom (unable to read the checklist) and the underlying issue (inability to read the controls and evaluate special/global functions when the mixer is not running).
Per #2256 (comment), this is an rough overview of how things should look:
Expected Behavior
That you should be able to still evaluate inputs, special/global functions, that do not inherently rely on the mixer. For example, physical controls should be read outside the mixer task, in its own task. Special/global functions that don't inherently rely on the mixer (i.e. due to input/mixes/output sources being input or somehow interacting with the RF) should be able to always be evaluated also.