[CAS] Consolidate compile cache flags

Rename `-enable-cas` to `-compile-cache-job` to align with clang option
names and promote that to a new driver only flag.

Few other additions to driver flag for caching behaviors:
* `-compile-cache-remarks`: now cache hit/miss remarks are guarded behind
  this flag
* `-compile-cache-skip`: skip replaying from the cache. Useful as a
  debugging tool to do the compilation using CAS inputs even the output
  is a hit from the cache.

include/swift/Frontend/CachingUtils.h

@@ -39,7 +39,7 @@ bool replayCachedCompilerOutputs(
     llvm::cas::ObjectStore &CAS, llvm::cas::ActionCache &Cache,
     llvm::cas::ObjectRef BaseKey, DiagnosticEngine &Diag,
     const FrontendInputsAndOutputs &InputsAndOutputs,
-    CachingDiagnosticsProcessor &CDP);
+    CachingDiagnosticsProcessor &CDP, bool CacheRemarks);
 
 /// Load the cached compile result from cache.
 std::unique_ptr<llvm::MemoryBuffer> loadCachedCompileResultFromCacheKey(