Describe the bug

We should use actions/cache to improve build speeds and resiliency against temporary flakiness on external dependencies.

The following things to check come to mind:

• aqt: Can keep downloaded archives, but won't re-use them. Caching the whole Qt directories for that reason now.
• choco: Hardcoding a cacheLocation now
• brew: not used
• pip: Different paths for Windows/Mac
• Android SDK & NDK
• brew if added via Switch to create-dmg #2207 Tracked in Build: Cache Mac's brew install (create-dmg) #2412

Depends on #2276 to avoid caching a bad state.

To Reproduce

Random flakiness such as Qt download failures.

Expected behavior

Dependencies should be cached. Temporary download failures should not break the build.

Screenshots

https://github.com/jamulussoftware/jamulus/runs/4936344409?check_suite_focus=true

Caught ArchiveConnectionError, terminating installer workers
Failure to connect to https://download.qt.io/online/qtsdkrepository/windows_x86/desktop/qt5_5152/qt.qt5.5152.win64_msvc2019_64/5.15.2-0-202011130602qtremoteobjects-Windows-Windows_10-MSVC2019-Windows-Windows_10-X86_64.7z.sha1: ReadTimeout

Additional context

https://docs.github.com/en/actions/advanced-guides/caching-dependencies-to-speed-up-workflows
https://github.com/actions/cache