JIT: Avoid unnecessary GTF_GLOB_REFs (#84349)

JIT: Avoid unnecessary GTF_GLOB_REFs (#84349)

* Avoid setting GTF_GLOB_REF on GT_FIELD_ADDR nodes
* Avoid setting GTF_GLOB_REF on GT_FIELD nodes off of implicit byrefs.
  This is ok now since implicit byref morphing indiscriminately sets
  GTF_GLOB_REF for these.
* Manually clone a "pointer to span" in span intrinsic expansion when it points to a local. Unfortunately this does not fall out from the above since gtClone does not handle FIELD_ADDR, and making it handle this needs some more work.

These changes are necessary to avoid address exposure in the two user
benchmarks in #83388.

Fix #74563
Fix #856