JIT: improve simplification of IND(ADDR(x)) (dotnet/coreclr#20508)

JIT: improve simplification of IND(ADDR(x)) (dotnet/coreclr#20508)

Some `IND(ADDR(x))` trees were not being optimized to `x` by morph,
particularly when `x` was the promoted pointer field of a `Span`.
Instead they were creating local fields that blocked enregistration
and lead to store-load pairs like:

```asm
       mov      bword ptr [rsp+20H], rax
       mov      rax, bword ptr [rsp+20H]
```

Add logic to `fgMorphSmpOp`'s `GT_IND` clause to recognize and simplify
these cases.

Commit migrated from https://github.com/dotnet/coreclr/commit/c0aa74fe584a04f8c7c8e81882793a136ee074d9