Optimizer: move optimizer bridging code from PassManager.cpp into its own file.

The bridging code was in PassManager.cpp only for historical reasons.
It's now in OptimizerBridging.cpp.

NFC

Author: eeckstein

include/swift/SILOptimizer/PassManager/PassManager.h

@@ -450,6 +450,7 @@ class SILPassManager {
 
   static bool isPassDisabled(StringRef passName);
   static bool isInstructionPassDisabled(StringRef instName);
+  static bool isAnyPassDisabled();
   static bool disablePassesForFunction(SILFunction *function);
 
   /// Runs the SIL verifier which is implemented in the SwiftCompilerSources.