[Preferences Refactor] Remove window size combo box from graphics preferences

Windows can be resized on their own, we do not need this box
This should also fix window resizing when applying preferences.
[Preferences Refactor] Handle Hardware tab earlier to avoid early return when custom isn't displayed
[Preferences Refactor] Further cleanup

Moves to visibility_control and enabled_control instead of using callbacks, this lightens the load on opening preferences, and makes them responsive even to debug settings changes
Removes the moving m for meter text with draw distance, I don't think anyone cares if it's a little to the side of the number.
Adjustment of tabs to spaces in xml.
Return early when disabling unavailable settings if shaders are unavailable.
Cuts back on single-call functions in favor of direct binds.
[Preferences Refactor] Cleanup on llfloaterpreferences

Moves to calling refreshEnabledState directly from LLPanelDisplay instead of bouncing around in LLFloaterPreferences first or using static proxy functions
Cleans up unused cached button pointers and old style static callbacks.