Use the `Base` type alias from
https://github.com/llvm/llvm-project/pull/158433.

Current convertVectorToMMAOps starts from vector.contract and finds its
dependencies as the targets to convert. In GPU dialect, we have
gpu.subgroup_mma_elementwise operation. We should be able to lower
element-wise operations to GPU MMA operations without vector.contract.
This patch adds this case to the pattern.

This patch updates the following ops to use `source` (instead of
`vector`) as the name for their source argument:
  * `vector.extract`
  * `vector.scalable.extract`
  * `vector.extract_strided_slice`

This change ensures naming consistency with the "builders" for these Ops
that already use the name `source` rather than `vector`. It also
addresses part of:
  * https://github.com/llvm/llvm-project/issues/131602

Specifically, it ensures that we use `source` and `dest` for read and
write operations, respectively (as opposed to `vector` and `dest`).

See https://github.com/llvm/llvm-project/pull/147168 for more info.

See https://github.com/llvm/llvm-project/pull/147168 for more info.

Add conversion for broadcast from scalar for LLVM and SPIRV. Also some
miscellaneous replacements of vector.splat with vector.broadcast in
VectorToGPU and ArithToAMDGPU.

Part of deprecation of vector.splat RFC:
https://discourse.llvm.org/t/rfc-mlir-vector-deprecate-then-remove-vector-splat/87143/4

These are identified by misc-include-cleaner.  I've filtered out those
that break builds.  Also, I'm staying away from llvm-config.h,
config.h, and Compiler.h, which likely cause platform- or
compiler-specific build failures.

This patch fixes warnings of the form:

  mlir/lib/Conversion/VectorToGPU/VectorToGPU.cpp:320:19: error:
  unused variable 'result' [-Werror,-Wunused-variable]