Fix step with stackalloc (dotnet/coreclr#27246)

Fix step with stackalloc (dotnet/coreclr#27246)

* Make ControllerStackInfo::m_returnFrame private

* Make ControllerStackInfo always capture a return frame

In case the active frame has no managed caller, capture
the unmanaged frame

* Fix step over stackalloc

Generalize handling of stack allocations and stepping

* Fix GetFunctionFromToken() argument checking

Check token type is a method before creating a CordbFunction.

Add extra assert to check for invalid tokens

Commit migrated from https://github.com/dotnet/coreclr/commit/551710b95a0aa795f42750966a199c26cc9cd0d9