Optimize generated function inlining (#7811)

Previously V3InlineCFuncs inlined call sites but never deleted the now
dead callees. Also missed a lot of opportunities due to evaluation order.

Rewrite using a graph based algorithm, using only a single traversal of
the netlist. This is clearer, more accurate, and faster at compile time.

Also add a clean -fno-inline-cfuncs disable. Setting the limits to 0
still disables inlining, except of empty functions, which can be inlined
with 0 limits (they are no ops). It will also prune unused functions
without -fno-inline-cfuncs.

Pass now also respects `--output-split`

src/V3TraceDecl.cpp

@@ -980,6 +980,7 @@ public:
         AstCFunc* rootFuncp = nullptr;
         if (!v3Global.opt.libCreate().empty()) {
             rootFuncp = newCFunc(flp, "trace_init_root");
+            rootFuncp->entryPoint(true);
             for (size_t i = 0; i < m_topScopeRootFuncCount; ++i) {
                 AstCCall* const callp = new AstCCall{flp, topScopeFuncps.at(i)};
                 callp->dtypeSetVoid();
@@ -1017,6 +1018,7 @@ public:
         // Set name of top level function
         AstCFunc* const topFuncp = m_topFuncps.front();
         topFuncp->name("trace_init_top");
+        topFuncp->entryPoint(true);
 
         if (rootFuncp && v3Global.opt.debugCheck()) checkCallsRecurse(rootFuncp);
         checkCalls(topFuncp);