All the store-like atomics are missing from GenTree::OperExceptions, even as they can throw NREs. I noticed this when implementing downstream support for them (and, in fact, this bug blocks that support).

The plan for fixing is as follows:

1. Make all atomics (including GT_CMPXCHG) GenTreeIndir-derived.
2. This will automatically "do the right thing" in a lot of places; however, all uses of OperIsIndir will need to be audited.
3. Add the missing opcodes to GenTree::OperExceptions.