Adds support for both CFI and KCFI for attaching concrete and abstract
types to functions. KCFI does this through generation of `ReifyShim` on
any function pointer that could go in a vtable, and checking the
`ReifyReason` when emitting the instance. CFI does this by attaching
both the concrete and abstract type to every instance.
TypeID codegen tests are switched to be anchored on the left rather than
the right in order to allow emission of additional type attachments.
Fixes#115953
Fix casting between methods and function pointers by assigning a
secondary type id to methods with their concrete self so they can be
used as function pointers.
