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/V3Scope.cpp

@@ -36,13 +36,13 @@
 //######################################################################
 // Scope class functions
 
-class ScopeVisitor final : public AstNVisitor {
+class ScopeVisitor final : public VNVisitor {
 private:
     // NODE STATE
     // AstVar::user1p           -> AstVarScope replacement for this variable
     // AstTask::user2p          -> AstTask*.  Replacement task
-    const AstUser1InUse m_inuser1;
-    const AstUser2InUse m_inuser2;
+    const VNUser1InUse m_inuser1;
+    const VNUser2InUse m_inuser2;
 
     // TYPES
     // These cannot be unordered unless make a specialized hashing pair (gcc-8)
@@ -320,7 +320,7 @@ public:
 //######################################################################
 // Scope cleanup -- remove unused activates
 
-class ScopeCleanupVisitor final : public AstNVisitor {
+class ScopeCleanupVisitor final : public VNVisitor {
 private:
     // STATE
     AstScope* m_scopep = nullptr;  // Current scope we are building