Move to U22/GCC12/macOS10.15

[baconpaul]

Just a placeholder

• get new docker image working. Got it started but it didn't run.
• push macOS to 10.15
• set force filesystem on
• consider making filesystem fail a warning to fallback in plugininfra
• etc

[mthierman]

This reverts the concepts workaround in tuning-library once we can use <filesystem>: surge-synthesizer/tuning-library@main...mthierman:tuning-library:feature/path

[baconpaul]

#8255 dd this and i confirmed that all platforms are using std::filesystem (by adding a message to plugininfra)

@mthierman I'm gonna leave this open so you can remember that diff but I think that's now safe to apply all platforms.