Qt/Controllers: Refresh GUI on settings change.

[AdmiralCurtiss]

(without triggering signals)

Prep work for allowing opening the Controller settings mid-Netplay without everything breaking. See #11070 (comment).

To be clear, the intent of this PR is having the Controller GUI properly reflect the current state if it's changed programmatically by Netplay (or anything else). The eventual target (not in this PR) is that during Netplay, the dropdowns for the GC controller ports and Wiimotes will be greyed out (because we don't support them changing mid-session), but the Configure buttons next to them will still work so you can change your mappings, along with harmless-to-Netplay settings like Background Input.

[iwubcode]

Untested but code looks good. Nice work!

[iwubcode]

Ok, did a bit of testing to complete this. Not noticing any regressions or other issues.

[AdmiralCurtiss]

Alright then.

[shuffle2]

Supposedly this causes a crash: https://bugs.dolphin-emu.org/issues/13141

[shuffle2]

@AdmiralCurtiss do you know if this PR caused the threading issues seen in that issue? Or does this PR just happen to make it more obvious? If the former, maybe this PR should be reverted (and Config Add/Remove should be noted as not thread safe).

[shuffle2]

note however, that the Config stuff seems to be broken even without threading issues: since Add/Remove can be called recursively, you either wind up with iterators into s_callbacks being invalidated, or recursive calls getting silently dropped (the current behavior has OnConfigChanged returning early). I'm not sure dropping the recursion is actually good? It means that if a Config change occurs while walking s_callbacks, the previously invoked callbacks won't see the new change...right?

[AdmiralCurtiss]

I'll have to look at it in detail, but yeah the entire system is a bit sketchy...