[NativeAOT-LLVM] Optimize PI and RPI transitions

[SingleAccretion]

See the commit message for details on the ABI changes. The main idea is to make our PI transition frame "zero-sized" by defining it to be equal to the shadow stack top.

Diffs (WasmDebugging, browser):

Summary of Code Size diffs:
(Lower is better)

Total bytes of base: 647755
Total bytes of diff: 646660
Total bytes of delta: -1095 (-0.17% % of base)
Average relative delta: -16.24%
    diff is an improvement
    average relative diff is an improvement

Top method regressions (percentages):
          21 (161.54% of base) : 1001.dasm - Thread::Destroy()
          45 (56.96% of base) : 1000.dasm - Thread::Construct()
          27 (20.77% of base) : 1006.dasm - RhpReversePInvoke
          15 (13.27% of base) : 1002.dasm - Thread::GcScanRoots(void (*)(Object**, ScanContext*, unsigned int), ScanContext*)
           7 ( 6.80% of base) : 1003.dasm - RhpWaitForGC2
           1 ( 2.63% of base) : 1009.dasm - RhpPInvokeReturn

Top methods only present in diff:
         211 (     ∞ of base) : 1053.dasm - RhpReversePInvokeAndPushSparseVirtualUnwindFrame
         184 (     ∞ of base) : 1052.dasm - Thread::ReversePInvokeAttachOrTrapThread_Wasm(unsigned long)
          33 (     ∞ of base) : 1054.dasm - RhpReversePInvokeReturnAndPopSparseVirtualUnwindFrame
          22 (     ∞ of base) : 1051.dasm - Thread::GetTransitionFrame()

Top method improvements (percentages):
         -57 (-78.08% of base) : 1024.dasm - S_P_CoreLib_System_Runtime_GCStress__Initialize
         -22 (-62.86% of base) : 1008.dasm - RhpPInvoke
         -45 (-55.56% of base) : 1047.dasm - S_P_CoreLib_System_Threading_Thread__LongSpinWait
         -45 (-55.56% of base) : 1033.dasm - S_P_CoreLib_Interop_Sys__LowLevelMonitor_Release
         -45 (-55.56% of base) : 1017.dasm - S_P_CoreLib_Interop_Sys__Free
         -45 (-52.94% of base) : 1016.dasm - S_P_CoreLib_System_Runtime_InternalCalls__RhGetGcTotalMemory
         -43 (-51.81% of base) : 1014.dasm - S_P_CoreLib_System_Runtime_InternalCalls__RhEndNoGCRegion
         -43 (-50.00% of base) : 1043.dasm - S_P_CoreLib_System_Threading_Thread__Yield
         -45 (-48.91% of base) : 1018.dasm - S_P_CoreLib_System_Runtime_InternalCalls__RhCollect
         -45 (-42.86% of base) : 1015.dasm - S_P_CoreLib_System_Runtime_InternalCalls__RhStartNoGCRegion
         -45 (-41.28% of base) : 1042.dasm - S_P_CoreLib_System_Runtime_InteropServices_NativeMemory__Alloc_0
         -43 (-40.19% of base) : 1037.dasm - S_P_CoreLib_Internal_Runtime_FrozenObjectHeapManager__ClrVirtualReserve
         -41 (-39.81% of base) : 1046.dasm - S_P_CoreLib_System_Buffer___ZeroMemory
         -45 (-37.50% of base) : 1013.dasm - S_P_CoreLib_Internal_Runtime_CompilerHelpers_StartupCodeHelpers__InitializeModuleFrozenObjectSegment
         -41 (-37.27% of base) : 1044.dasm - S_P_CoreLib_System_Buffer___Memmove
          -9 (-36.00% of base) : 1007.dasm - RhpReversePInvokeReturn
         -41 (-31.78% of base) : 1031.dasm - S_P_CoreLib_System_Threading_LowLevelMonitor__DisposeCore
         -41 (-28.47% of base) : 1038.dasm - S_P_CoreLib_Internal_Runtime_Augments_RuntimeAugments__InitializeStackTraceIpMap
         -51 (-24.76% of base) : 1027.dasm - S_P_CoreLib_System_Threading_LowLevelLock__SignalWaiter
         -43 (-24.57% of base) : 1035.dasm - S_P_CoreLib_System_Threading_LowLevelMonitor__Initialize

Top methods only present in base:
         -66 (-100.00% of base) : 1005.dasm - RhpGetOrInitShadowStackTop
         -15 (-100.00% of base) : 1004.dasm - RhpReversePInvokeAttachOrTrapThread2

55 total methods with Code Size differences (45 improved, 10 regressed)

Contributes to #3163.