Ruby: Remove CacheMsg class from SLICC

The goal of the patch is to do away with the CacheMsg class currently in use
in coherence protocols. In place of CacheMsg, the RubyRequest class will used.
This class is already present in slicc_interface/RubyRequest.hh. In fact,
objects of class CacheMsg are generated by copying values from a RubyRequest
object.

src/mem/protocol/MI_example-cache.sm

@@ -181,9 +181,9 @@ machine(L1Cache, "MI Example L1 Cache")
   }
 
     // Mandatory Queue
-  in_port(mandatoryQueue_in, CacheMsg, mandatoryQueue, desc="...") {
+  in_port(mandatoryQueue_in, RubyRequest, mandatoryQueue, desc="...") {
     if (mandatoryQueue_in.isReady()) {
-      peek(mandatoryQueue_in, CacheMsg, block_on="LineAddress") {
+      peek(mandatoryQueue_in, RubyRequest, block_on="LineAddress") {
 
         Entry cache_entry := getCacheEntry(in_msg.LineAddress);
         if (is_invalid(cache_entry) &&
@@ -281,7 +281,7 @@ machine(L1Cache, "MI Example L1 Cache")
   }
 
   action(p_profileMiss, "p", desc="Profile cache miss") {
-    peek(mandatoryQueue_in, CacheMsg) {
+    peek(mandatoryQueue_in, RubyRequest) {
       cacheMemory.profileMiss(in_msg);
     }
   }