This commit changes the LLVM dialect's CAPI pointer getters to drop
support for typed pointers. Typed pointers are deprecated and should no
longer be generated.
This moves the `LLVMArrayType` to a `TypeDef`. The main side-effect of
this change is that the syntax `array<4xi32>` is no longer allowed. It
was previously parsed and then printed as `array<4 x i32>`. Now the
syntax must be the latter.
Reviewed By: rriddle
Differential Revision: https://reviews.llvm.org/D136473