[NFC] Rename “DeclPath” -> “AccessPath”

To avoid ambiguity, ImportResolution and a few other things used the term “decl path” instead of “access path”. Switch back to the correct terminology now that the compiler is becoming more consistent about it.

include/swift/AST/Decl.h

@@ -1514,7 +1514,7 @@ public:
     return getImportPath().getModulePath(getImportKind());
   }
 
-  ImportPath::Access getDeclPath() const {
+  ImportPath::Access getAccessPath() const {
     return getImportPath().getAccessPath(getImportKind());
   }