Refactor V3Delayed to enable algorithmic extension (#5090)

No functional change.

This patch is just cleanup with some non-functional changes to enable
the next patch. Most importantly createDlyOnSet, which implements NBAs
for arrays, has a new streamlined implementation that does the same
thing. Some output code is perturbed due to statement/local variable
insertion order.

Also renamed Vdlyvfoo to VdlyFoo for easier readability of the generated
code.

src/V3AstNodeOther.h

@@ -2434,13 +2434,11 @@ public:
     ASTGEN_MEMBERS_AstAlwaysObserved;
 };
 class AstAlwaysPost final : public AstNodeProcedure {
-    // Like always but post assignments for memory assignment IFs
-    // @astgen op1 := sensesp : Optional[AstSenTree] // Sensitivity list iff clocked
+    // Like always but 'post' scheduled, e.g. for array NBA commits
+
 public:
-    AstAlwaysPost(FileLine* fl, AstSenTree* sensesp, AstNode* stmtsp)
-        : ASTGEN_SUPER_AlwaysPost(fl, stmtsp) {
-        this->sensesp(sensesp);
-    }
+    AstAlwaysPost(FileLine* fl)
+        : ASTGEN_SUPER_AlwaysPost(fl, nullptr) {}
     ASTGEN_MEMBERS_AstAlwaysPost;
 };
 class AstAlwaysPostponed final : public AstNodeProcedure {

src/V3SchedVirtIface.cpp

@@ -128,7 +128,7 @@ private:
         if (writesToVirtIface(nodep)) {
             // Convert to always, as we have to assign the trigger var
             FileLine* const flp = nodep->fileline();
-            AstAlwaysPost* const postp = new AstAlwaysPost{flp, nullptr, nullptr};
+            AstAlwaysPost* const postp = new AstAlwaysPost{flp};
             nodep->replaceWith(postp);
             postp->addStmtsp(
                 new AstAssign{flp, nodep->lhsp()->unlinkFrBack(), nodep->rhsp()->unlinkFrBack()});