Streamline dump control options

- Rename `--dump-treei` option to `--dumpi-tree`, which itself is now a
  special case of `--dumpi-<tag>` where tag can be a magic word, or a
  filename
- Control dumping via static `dump*()` functions, analogous to `debug()`
- Make dumping independent of the value of `debug()` (so dumping always
  works even without the debug flag)
- Add separate `--dumpi-graph` for dumping V3Graphs, which is again a
  special case of `--dumpi-<tag>`
- Alias `--dump-<tag>` to `--dumpi-<tag> 3` as before

src/V3InstrCount.cpp

@@ -24,6 +24,8 @@
 
 #include <iomanip>
 
+VL_DEFINE_DEBUG_FUNCTIONS;
+
 /// Estimate the instruction cost for executing all logic within and below
 /// a given AST node. Note this estimates the number of instructions we'll
 /// execute, not the number we'll generate. That is, for conditionals,
@@ -254,7 +256,6 @@ private:
         iterateChildren(nodep);
     }
 
-    VL_DEBUG_FUNC;  // Declare debug()
     VL_UNCOPYABLE(InstrCountVisitor);
 };
 
@@ -290,7 +291,7 @@ private:
         }
         --m_depth;
     }
-    VL_DEBUG_FUNC;  // Declare debug()
+
     VL_UNCOPYABLE(InstrCountDumpVisitor);
 };