[passmanager] Move SILOptimizerRequests.cpp into ./lib/SILOptimizer/PassManager/*

I am doing this move for two reasons:

1. This file only works directly with parts of the PassManager.
2. In the SILOptimizer, we do not have files in the top level of the file tree
and instead group them in one of the subject subfolders.

Author: gottesmm

lib/SILOptimizer/CMakeLists.txt

@@ -34,7 +34,6 @@ add_subdirectory(UtilityPasses)
 add_subdirectory(Utils)
 
 add_swift_host_library(swiftSILOptimizer STATIC
-  SILOptimizerRequests.cpp
   ${SILOPTIMIZER_SOURCES})
 target_link_libraries(swiftSILOptimizer PRIVATE
   swiftSIL)

lib/SILOptimizer/PassManager/CMakeLists.txt

@@ -3,4 +3,5 @@ silopt_register_sources(
   Passes.cpp
   PassPipeline.cpp
   PrettyStackTrace.cpp
+  SILOptimizerRequests.cpp
 )