Updated to latest JUCE

[kcoul]

Maybe better to use as a reference to update JUCE to latest yourself if you want to, since we are both using custom forks.
I needed to do this since older JUCE won't compile anymore on Sequoia due to certain functions being made obsolete.

Here's what I changed:

1. Swapped in my fork of latest JUCE
2. Updated minimum macOS from 10.10 to 10.11
3. Re-applied urlOpened patch for iOS
4. Broke up platform-specific defs in CMakeLists.txt for Desktop targets, since cross-compilation is unlikely for these
5. Commented out breaking changes in LookAndFeel classes
6. Fixes some asserts in Parameter CTORs
7. 1 fix and 1 comment-out for Thread priority, JUCE might have a regression here for AudioThumbnailCache since there's no way to elevate the priority in a nested Thread as far as I can tell.
8. Miscellaneous other minor changes