[RemarkUtil] Refactor llvm-remarkutil to include size-diff

This change follows from https://reviews.llvm.org/D156416 We include
`llvm-remark-size-diff` as a part of `llvm-remarkutil` under a
subcommand `size-diff`.

Differential Revision: https://reviews.llvm.org/D156515

Author: Zain Jaffal

clang/docs/ClangFormattedStatus.rst

@@ -5869,11 +5869,6 @@ tree in terms of conformance to :doc:`ClangFormat` as of: March 06, 2022 17:32:2
      - `39`
      - `1`
      - :part:`97%`
-   * - llvm/tools/llvm-remark-size-diff
-     - `1`
-     - `1`
-     - `0`
-     - :good:`100%`
    * - llvm/tools/llvm-rtdyld
      - `1`
      - `0`

clang/docs/tools/clang-formatted-files.txt

@@ -7142,7 +7142,6 @@ llvm/tools/llvm-reduce/deltas/ReduceOperandsToArgs.cpp
 llvm/tools/llvm-reduce/deltas/ReduceOperandsToArgs.h
 llvm/tools/llvm-reduce/deltas/ReduceSpecialGlobals.cpp
 llvm/tools/llvm-reduce/deltas/ReduceSpecialGlobals.h
-llvm/tools/llvm-remark-size-diff/RemarkSizeDiff.cpp
 llvm/tools/llvm-rust-demangle-fuzzer/DummyDemanglerFuzzer.cpp
 llvm/tools/llvm-rust-demangle-fuzzer/llvm-rust-demangle-fuzzer.cpp
 llvm/tools/llvm-shlib/libllvm.cpp

llvm/docs/CommandGuide/index.rst

@@ -96,5 +96,4 @@ Remarks Tools
 .. toctree::
    :maxdepth: 1
 
-   llvm-remark-size-diff
    llvm-remarkutil