[llvm] Remove the Legacy PM Hello example (#95708)

The Legacy PM was deprecated for the optimization pipeline in LLVM 14
[1] (the support was removed altogether in the following release). This
patch removes the original Hello example that was introduced to
illustrate the Legacy PM. The Hello example no longer works and hence is
deleted. The corresponding documentation is also removed.

Note, Hello example for the new PM is located in
  * llvm/lib/Transforms/Utils/HelloWorld.cpp
  
and documented in
  * WritingAnLLVMNewPMPass.rst.

[1]
https://releases.llvm.org/14.0.0/docs/ReleaseNotes.html#changes-to-the-llvm-ir

Author: banach-space

clang-tools-extra/test/CMakeLists.txt

@@ -74,17 +74,8 @@ if (NOT WIN32 OR NOT LLVM_LINK_LLVM_DYLIB)
       PLUGIN_TOOL clang-tidy)
 endif()
 
-if(CLANG_BUILT_STANDALONE)
-  # LLVMHello library is needed below
-  if (EXISTS ${LLVM_MAIN_SRC_DIR}/lib/Transforms/Hello
-      AND NOT TARGET LLVMHello)
-    add_subdirectory(${LLVM_MAIN_SRC_DIR}/lib/Transforms/Hello
-      lib/Transforms/Hello)
-  endif()
-endif()
-
 if(TARGET CTTestTidyModule)
-    list(APPEND CLANG_TOOLS_TEST_DEPS CTTestTidyModule LLVMHello)
+    list(APPEND CLANG_TOOLS_TEST_DEPS CTTestTidyModule)
     target_include_directories(CTTestTidyModule PUBLIC BEFORE "${CLANG_TOOLS_SOURCE_DIR}")
     if(CLANG_PLUGIN_SUPPORT AND (WIN32 OR CYGWIN))
       set(LLVM_LINK_COMPONENTS

clang-tools-extra/test/clang-tidy/CTTestTidyModule.cpp

@@ -1,5 +1,5 @@
 // REQUIRES: plugins
-// RUN: clang-tidy -checks='-*,mytest*' --list-checks -load %llvmshlibdir/CTTestTidyModule%pluginext -load %llvmshlibdir/LLVMHello%pluginext | FileCheck --check-prefix=CHECK-LIST %s
+// RUN: clang-tidy -checks='-*,mytest*' --list-checks -load %llvmshlibdir/CTTestTidyModule%pluginext | FileCheck --check-prefix=CHECK-LIST %s
 // CHECK-LIST: Enabled checks:
 // CHECK-LIST-NEXT:    mytest1
 // CHECK-LIST-NEXT:    mytest2