Tweak ObjectStackAllocationTests so that they work correctly under crossgen2 (#40096)

Tweak ObjectStackAllocationTests so that they work correctly under crossgen2 (#40096)

- Add a mechanism for passing arbitrary arguments to the crossgen2 process while running crossgen2 tests
- Pass the `--codegenopt JitObjectStackAllocation=1` when compiling this test with Crossgen2. This will result in enabling the object stack allocation feature during compilation
- As Crossgen2 currently disregards the debuggable attribute when deciding codegen mode, detect the presence running crossgen2 and expect allocation to occur on the stack even if S.P.C is debuggable