This allows LiveRadio drivers to use the single serial connection as
if it has exclusive access by making sure that only one RadioJob runs
at any given time. This could potentially reduce performance if you
were doing lots of operations against multiple live radios at once,
and we could improve that later. However, it makes writing LiveRadio
drivers with multiple sub_devices much more straightforward.

Since live radios don't have a comment column (even with metadata
simulation) we cannot assume it is there for calculating the index for
extra columns.

Note this does not implement any D-STAR stuff or satellite memories
yet, it's just basic support.

Fixes #10018

This is sort of an approximation as we don't have a good way to
support pairs of full memories stored together, but it's probably
close enough.

Related to #10018

Fixes #11459
Fixes #11259

These radios (annoyingly) treat frequencies in airband as AM, which
really isn't how chirp was designed to work. Before, we were making
them immutable, but that brings all sorts of problems with it. Instead,
coerce the values on get/set, and return a warning from
validate_memory() so the user is warned.

In reality, we should probably be doing that more places where we have
immutable fields, where the immutable-ness depends on the content of
the memory (i.e the frequency) than the location.

Fixes: #11441

This prevented import_mem from working and thus paste (!)

Fixes #11455