Library controller navigation fixes & enhancements

[ronso0]

I attempt to clean up my outdated previous PR to clear search via controllers with [Library],GoToItem, as well as some small improvements for library controller navigation.

reworked and rebased since noone reviewed it anyways so far
I hope the commits are easy to review because I think this solves some issues with basic Library navigation that would ease the library/controller UX in 2.3

https://bugs.launchpad.net/mixxx/+bug/1840541

don't allow to focus Library feature buttons
... in Recording, AutoDJ, Analysis, Hidden or Missing neither with Tab key on keyboard nor [Library]MoveFocus... to always see the focus indicating border on the sidebar or tracks table.
There's no point in having those focused as there's no way to trigger them, neither from keyboard or controllers. For AutoDJ and Recording there are keyboard shortcuts.

fix hasFocus()
... in DlgRecording, DlgAutoDJ, DlgAnalysis, DlgHidden and DlgMissing to prevent 'refocus Library' calls there before issuing a move/scroll command.

Prevent focus from getting stuck at Clear button
In master, the focus can be moved to the Clear button with [Library],MoveFocus[Backward, Forward] (when there is an active search). Then, MoveFocusForward would do nothing because behind the scenes library control tests if the sidebar or tracks table have focus; if false it would try to re-focus the tracks table: focus the sidebar > emulate Tab > then send the MoveFocus Tab = we end up at the Clear button again. With MoveFocus, -1 it would jump between sidebar and Clear button.
Now, the focus controls always send a Tab key no matter which widget has focus.

Clear Search from controller
Clear the seach with [Library],GoToItem when either the searchbox or the Clear button has focus.

ToDo

• clean up, remove debug output
• remove focusAnalysis()
• resolve conflicts
• add some skin feedback: dim border for WTextBrowser, ...

[ronso0]

maybe this doesn't need to be a separate function, until now we need it only twice here.

[ronso0]

unchanged

[ronso0]

unchanged

[ronso0]

After GoToItem > Clear Search we could also automatically jump to the tracks table.
I guess someone clearing the search via controller wants to see and scroll all available tracks with it, rather than refining the search which she/he needs the keyboard for anyway.

[Be-ing]

I guess someone clearing the search via controller wants to see and scroll all available tracks with it, rather than refining the search which she/he needs the keyboard for anyway.

I don't think that's safe to guess. Clearing the search from a controller then reaching to the keyboard to type seems like a reasonable thing to do IMO.

[ronso0]

don't allow to focus Library feature buttons
... in Recording, AutoDJ, Analysis, Hidden or Missing neither with Tab key on keyboard nor [Library]MoveFocus... to always see the focus indicating border on the sidebar or tracks table.
There's no point in having those focused as there's no way to trigger them, neither from keyboard or controllers. For AutoDJ and Recording there are keyboard shortcuts.

Any objections?
Tab / MoveFocus now always moves focus between tree view and tracks tables (and Clear search button). No need to Tab through a row of buttons anymore, like in AutoDJ.
BUT I don't know if someone actually makes use of Tab, Enter and Space to navigate library features like web pages, maybe a visually impaired user? if at all, this wouldn't work now anymore. we can revert that commit later on. Edit and add focus highights to every skin

[ronso0]

Closed and split up for easy review
#2597
#2598
#2599