[RyuJit/WASM] Longer-term TODOs

[SingleAccretion]

A list of things that will need to be fixed before the work can be considered functional:

1. genPoisonFrame implementation.
2. Stack alignment in lvaAlignFrame.
3. [Wasm RyuJit] local stores #122390 - remove code from STORE_LCL_VAR codegen that deals with non-candidates, add asserts to such effect.
   • Once we have some minimal RA.
4. Fix untracked debug scopes in siOpenScopesForNonTrackedVars.
   • [Wasm RyuJit] Fixes for some issues in codegen bringup tests #122483
5. Remove #ifdef TARGET_WASM from the JMC insertion path since once we have proper WASM CG2 collections and/or call emit support.
   • [Wasm RyuJit] Fixes for some issues in codegen bringup tests #122483
6. Fix the single-IG restriction of the prolog so that we don't need to worry about methods with a large number of non-enregistered arguments overflowing it. Ref: [RyuJit/WASM] Establish SP & FP and home register arguments #123270.
7. Set maxUncheckedOffset and related entries to zero; fix issues where the jit is relying on null checks for small offsets (see discussion here -- part of [Wasm RyuJit] throw helper / null check preliminaries #123053
8. There are many places in the JIT where we assume that constants must either be type I4 or type I and that's not the case for Wasm 32 bit. Figure out a way to systematically fix this.
9. Consider getting rid of GT_CNS_LONG so there is just one way to represent constant ints regardless of bitness.
10. Find all places that avoid creating bitcasts for !TARGET_64BIT and switch them to !LOWER_DECOMPOSE_LONGS instead.
11. Decide if we want to use a stack cookie to guard the shadow stack

Part of #121208.

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