JIT: Move call ABI determination earlier

[jakobbotsch]

We expect that this information will be necessary for heuristics for generalized promotion in relation to the passing of arguments. The generalized promotion is going to run before morph, so we will need to have access to this information.

Might be tricky with how the ABI determination happens at the same time as final args are added, so we may need to split this up in some way as well.

Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch
See info in area-owners.md if you want to be subscribed.

Issue Details

---

We expect that this information will be necessary for heuristics for generalized promotion in relation to the passing of arguments. The generalized promotion is going to run before morph, so we will need to have access to this information.

Might be tricky with how the ABI determination happens at the same time as final args are added, so we may need to split this up in some way as well.

Author:	jakobbotsch
Assignees:	-
Labels:	area-CodeGen-coreclr
Milestone:	-

[jakobbotsch]

This is relatively less important because the arguments that are actually passed in registers are currently almost always handled by regular promotion -- hitting the promotion limitations and also being able to be passed in a register is rare. Will move this to future.