Add integration tests after all:

[jheruty]

• Add simple integration test that validates code swapping works.
• Add integration tests to GitHub Actions.
• Add a user-configurable timeout to the compiler initialization. On GitHub actions, 5 seconds was insufficient (now defaults to 10 seconds).
• Add IsCompilerInitialized() function to Hotswapper, to allow waiting for compiler to load.
• Fix bug where a modified directory could be added as though it was a source file and break compilation.
• Add ability to swap out chunks of code between commented tags, for unit testing.
• Increase timeouts of compiler-related tests, due to GitHub Actions rarely running too slow and causing tests to fail.