Backfills the standard MIT X11 header on hand-written files that never
got one, attributing each to its first-commit author and year from git
history. Code vendored from dotnet/runtime and Humanizr/Humanizer gets
its origin's license lines and a provenance note instead. Generated
files (Resources.Designer.cs, the version-info template), tool-managed
suppression files, and BAML test-case fixtures intentionally stay
header-less.
Assisted-by: Claude:claude-fable-5:Claude Code
* We no longer maintain the weird `loadingAssemblies` global state.
* AssemblyList now internally handles multiple concurrent load requests for the same filename.
* AssemblyList.assemblies and its lock is now private to the AssemblyList.
* Removed a questionable caching layer (cache was per-AssemblyList, but was caching the result of a per-LoadedAssembly lookup function.
* Replaced static DisableAssemblyLoad() with bool-parameter on GetAssemblyResolver() call.