[mlir] Implement `DataLayoutTypeInterface` for `LLVMStructType`

Using this implementation of the interface it is possible to query the size, ABI alignment as well as the preferred alignment of a struct. It should yield the same results as LLVMs `llvm::DataLayout` on an equivalent `llvm::StructType`, including for packed structs.

Additionally it is also possible to increase the ABI and preferred alignment using a data layout entry with the type `llvm.struct<()>, which serves the same functionality as the `a:` component in LLVMs data layout string.

Differential Revision: https://reviews.llvm.org/D115600