[CIR] Add initial support for dynamic cast (#162337)
This adds support for dynamic cast handling and generating
`cir.dyn_cast` operations and `cir.dyn_cast_info` attributes.
This does not include support for lowering the dynamic cast to LLVM IR,
which will require changes to the LoweringPrepare pass that will be made
in a future change.
This also does not yet handle dynamic cast to void or exact dynamic
casts.
