Internals: Rename Ast on non-node classes (#3262). No functional change.

This commit has the following replacements applied:

	s/\bAstUserInUseBase\b/VNUserInUseBase/g;
        s/\bAstAttrType\b/VAttrType/g;
        s/\bAstBasicDTypeKwd\b/VBasicDTypeKwd/g;
        s/\bAstDisplayType\b/VDisplayType/g;
        s/\bAstNDeleter\b/VNDeleter/g;
        s/\bAstNRelinker\b/VNRelinker/g;
        s/\bAstNVisitor\b/VNVisitor/g;
        s/\bAstPragmaType\b/VPragmaType/g;
        s/\bAstType\b/VNType/g;
        s/\bAstUser1InUse\b/VNUser1InUse/g;
        s/\bAstUser2InUse\b/VNUser2InUse/g;
        s/\bAstUser3InUse\b/VNUser3InUse/g;
        s/\bAstUser4InUse\b/VNUser4InUse/g;
        s/\bAstUser5InUse\b/VNUser5InUse/g;
        s/\bAstVarType\b/VVarType/g;

src/V3Split.cpp

@@ -235,17 +235,17 @@ public:
 //######################################################################
 // Split class functions
 
-class SplitReorderBaseVisitor VL_NOT_FINAL : public AstNVisitor {
+class SplitReorderBaseVisitor VL_NOT_FINAL : public VNVisitor {
 private:
     // NODE STATE
     // AstVarScope::user1p      -> Var SplitNodeVertex* for usage var, 0=not set yet
     // AstVarScope::user2p      -> Var SplitNodeVertex* for delayed assignment var, 0=not set yet
     // Ast*::user3p             -> Statement SplitLogicVertex* (temporary only)
     // Ast*::user4              -> Current ordering number (reorderBlock usage)
-    const AstUser1InUse m_inuser1;
-    const AstUser2InUse m_inuser2;
-    const AstUser3InUse m_inuser3;
-    const AstUser4InUse m_inuser4;
+    const VNUser1InUse m_inuser1;
+    const VNUser2InUse m_inuser2;
+    const VNUser3InUse m_inuser3;
+    const VNUser4InUse m_inuser4;
 
 protected:
     // STATE
@@ -623,7 +623,7 @@ private:
 using ColorSet = std::unordered_set<uint32_t>;
 using AlwaysVec = std::vector<AstAlways*>;
 
-class IfColorVisitor final : public AstNVisitor {
+class IfColorVisitor final : public VNVisitor {
     // MEMBERS
     ColorSet m_colors;  // All colors in the original always block
 
@@ -681,7 +681,7 @@ private:
     VL_UNCOPYABLE(IfColorVisitor);
 };
 
-class EmitSplitVisitor final : public AstNVisitor {
+class EmitSplitVisitor final : public VNVisitor {
     // MEMBERS
     const AstAlways* const m_origAlwaysp;  // Block that *this will split
     const IfColorVisitor* const m_ifColorp;  // Digest of results of prior coloring
@@ -793,7 +793,7 @@ private:
     VL_UNCOPYABLE(EmitSplitVisitor);
 };
 
-class RemovePlaceholdersVisitor final : public AstNVisitor {
+class RemovePlaceholdersVisitor final : public VNVisitor {
     std::unordered_set<AstNode*> m_removeSet;  // placeholders to be removed
 public:
     explicit RemovePlaceholdersVisitor(AstNode* nodep) {