[NativeAOT] Unnecessary lookup in TrailingEpilogueInstructionsCount

[filipnavara]

UnixNativeCodeManager::TrailingEpilogueInstructionsCount for TARGET_ARM64 calls FindMethodInfo which is rather expensive. When called from UnixNativeCodeManager::GetReturnAddressHijackInfo it is already known so it can be passed over instead of doing extra lookup.

[jkotas]

cc @VSadov

[filipnavara]

There is room for other similar optimisations. For example, the codeManager->IsSafePoint also does the method lookup early in Thread::HijackCallback. That same method info could be used in codeManager->IsUnwindable debug-only ASSERT on ARM64. And it will inevitably be looked up again in Thread::HijackReturnAddress.

Some of these places are easier to patch than others but they all contribute to the signal handling response time when hijacking threads. That, in turn, contributes to GC pause times.