Remove redundant Transform.getName() definitions.

At some point, pass definitions were heavily macro-ized. Pass
descriptive names were added in two places. This is not only redundant
but a source of confusion. You could waste a lot of time grepping for
the wrong string. I removed all the getName() overrides which, at
around 90 passes, was a fairly significant amount of code bloat.

Any pass that we want to be able to invoke by name from a tool
(sil-opt) or pipeline plan *should* have unique type name, enum value,
commend-line string, and name string. I removed a comment about the
various inliner passes that contradicted that.

Side note: We should be consistent with the policy that a pass is
identified by its type. We have a couple passes, LICM and CSE, which
currently violate that convention.

lib/SILOptimizer/Transforms/CSE.cpp

@@ -1156,10 +1156,6 @@ class SILCSE : public SILFunctionTransform {
     }
   }
 
-  StringRef getName() override {
-    return RunsOnHighLevelSil ? "High-level CSE" : "CSE";
-  }
-  
 public:
   SILCSE(bool RunsOnHighLevelSil) : RunsOnHighLevelSil(RunsOnHighLevelSil) {}
 };