[Local GC] Break EE dependency on GC's generation table and alloc lock in single-proc scenarios (dotnet/coreclr#10065)
* Remove usage of the generation table from the EE by introducing an
EE-owned GC alloc context used for allocations on single-proc machines.
* Move the GC alloc lock to the EE side of the interface
* Repair the Windows ARM build
* Move the decision to use per-thread alloc contexts to the EE
* Rename the lock used by StartNoGCRegion and EndNoGCRegion to be more indicative of what it is protecting
* Address code review feedback 2 (enumerate the global alloc context as a part of GCToEEInterface)
* Code review feedback (3)
* Address code review feedback (move some GC-internal globals to gcimpl.h and gc.cpp)
* g_global_alloc_lock is a dword, not a qword - fixes a deadlock
* Move GlobalAllocLock to gchelpers.cpp and switch to preemptive mode when spinning
* Repair the Windows x86 build
Commit migrated from https://github.com/dotnet/coreclr/commit/
1b827b5a82f8c6f8a9ed760ee127938dea5a7ea4