Fix R2R failure in one of ObjectStackAllocation tests.

[erozenfeld]

AllocateSimpleClassAndCheckTypeNoHelper fails because
the object is allocated on the heap in R2R mode. The reason for that is
that we always use a helper for isinst in R2R mode and helper calls
cause us to assume the object escapes.

We don't have to use a helper in this case (even for R2R), #22086 tracks
fixing that.

For now the fix is not to check that the object was allocated on the stack
in this test case.

Fixes #22026.

[erozenfeld]

@sandreenko @echesakovMSFT @dotnet/jit-contrib PTAL

[erozenfeld]

@dotnet-bot test Windows_NT x64 Checked r2r_no_tiered_compilation
@dotnet-bot test Ubuntu x64 Checked r2r_no_tiered_compilation

[erozenfeld]

@dotnet-bot test OSX10.12 x64 Checked Innerloop Build and Test
@dotnet-bot test Ubuntu arm Cross Checked crossgen_comparison Build and Test
@dotnet-bot test Ubuntu x64 Checked Innerloop Build and Test (Jit - TieredCompilation=0)
@dotnet-bot test Ubuntu x64 Checked R2R Build and Test
@dotnet-bot test Ubuntu x64 Checked R2R no_tiered_compilation Build and Test
@dotnet-bot test Windows_NT x64 full_opt ryujit CoreCLR Perf Tests Correctness
@dotnet-bot test Windows_NT x64 min_opt ryujit CoreCLR Perf Tests Correctness
@dotnet-bot test Windows_NT x86 full_opt ryujit CoreCLR Perf Tests Correctness
@dotnet-bot test Windows_NT x86 min_opt ryujit CoreCLR Perf Tests Correctness