Merge tooltip strings for skins and controller wizard and maintain only one source

[jus]

Currently, we maintain 2 different string sources for tooltips:
* src/skin/tooltips.cpp
* src/controllers/controlpickermenu.cpp

Currently, we have the following quirks
* Same control different content in the tooltip
* Same control different spellings in the tooltip
* Control missing tooltip in one or another source

This is unnecessary work for code and translation contributors as well.
We have manifests for effects including a description, what about something similar in a centralized fashion for control descriptions?

[Be (be.ing)]

Should we deal with this for 2.1 or postpone it?

[Daniel Schürmann (daschuer)]

It is OK for me to postpone it.

[jus (jus)]

Do do not give it another 3 years.

[Be (be.ing)]

jus, unless you are committing to take care of this for 2.2, I don't think it is helpful to assign bugs to a milestone. This is how milestones accumulate a lot of noise, which makes it hard to tell what actually needs to get done to make a release happen.

[Daniel Schürmann (daschuer)]

Related:
https://bugs.launchpad.net/mixxx/+bug/1781827

[Swiftb0y (swiftb0y)]

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/7743