[RyuJIT] Ensure a test case and LSRA stress mode combo to have a multi-reg call node have its regs allocated in order reverse of ABI return order

[sivarv]

Source code pointer:
genStructReturn()

GT_RETURN(call) where call is a multi-reg call. ABI return reg order is {rax, rdx} or {xmm0, xmm1}. Under LSRA stress it could be possible that originally allocated regs are spilled and reloaded to reverse the order. But codegen of GT_RETURN needs to move the allocated regs as: rdx->rax and rax->rdx. This issue is to ensure that we have a test case and/or LSRA stress mode combo to hit that code path in codegen for testing.

category:correctness
theme:testing
skill-level:intermediate
cost:small
impact:small

[kunalspathak]

Will be good to have this, but at lower priority.