[mlir][tensor] NFC: name various Transforms/ files consistently

[antiagainst]

Summary

Use a suffix to make clear what the contents inside each file
are.

mlir/lib/Dialect/Tensor/Transforms/CMakeLists.txt

 add_mlir_dialect_library(MLIRTensorTransforms
   BufferizableOpInterfaceImpl.cpp
   Bufferize.cpp
-  ExtractSliceFromReshape.cpp
+  ExtractSliceFromReshapeUtils.cpp
   MergeConsecutiveInsertExtractSlicePatterns.cpp
-  SplitPadding.cpp
-  SwapExtractSliceWithProducer.cpp
+  SplitPaddingPatterns.cpp
+  SwapExtractSliceWithProducerPatterns.cpp
 
   ADDITIONAL_HEADER_DIRS
   ${MLIR_MAIN_INCLUDE_DIR}/mlir/Dialect/Tensor/Transforms
 
   DEPENDS
   MLIRTensorTransformsIncGen
 
   LINK_LIBS PUBLIC

mlir/lib/Dialect/Tensor/Transforms/ExtractSliceFromReshapeUtils.cpp

-//===- ExtractSliceFromReshape.cpp - Slice reshape rewrites-------*- C++-*-===//
+//===- ExtractSliceFromReshapeUtils.cpp - Slice reshape rewrites ----------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements rewrites that replace slices of reshape results with

mlir/lib/Dialect/Tensor/Transforms/SplitPaddingPatterns.cpp

-//===- SplitPadding.cpp - Splitting tensor.pad Op -------------------------===//
+//===- SplitPaddingPatterns.cpp - Splitting tensor.pad Op -----------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements patterns to wrap a tensor.pad op with an scf.if op

mlir/lib/Dialect/Tensor/Transforms/SwapExtractSliceWithProducerPatterns.cpp

-//===- SwapExtractSliceWithProducer.cpp - Swapping `tensor.extract_slice` ---=//
+//===- SwapExtractSliceWithProducerPatterns.cpp ---------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // Swap a `tensor.extract_slice` with the producer of the source if the producer