Add flag indicating HLL init status on CodeRef

Add a value that indicates whether the statevar in the coderef has been
assigned a value by the HLL (flag set via extop on HLL side).

This change is being made to coincide with a Rakudo development
regarding statevar initialization.

See [RT#102994](https://rt.perl.org/Public/Bug/Display.html?id=102994)

src/6model/reprs/MVMCode.c

@@ -69,6 +69,7 @@ static void gc_mark(MVMThreadContext *tc, MVMSTable *st, void *data, MVMGCWorkli
 static void gc_free(MVMThreadContext *tc, MVMObject *obj) {
     MVMCode *code_obj = (MVMCode *)obj;
     MVM_free(code_obj->body.state_vars);
+    MVM_free(code_obj->body.state_vars_is_hll_init);
 }
 
 static const MVMStorageSpec storage_spec = {

src/6model/reprs/MVMCode.h

@@ -6,6 +6,7 @@ struct MVMCodeBody {
     MVMObject      *code_object;
     MVMString      *name;
     MVMRegister    *state_vars;
+    MVMuint8       *state_vars_is_hll_init;
     MVMuint16       is_static;
     MVMuint16       is_compiler_stub;
 };

src/core/frame.c

@@ -568,6 +568,7 @@ void MVM_frame_invoke(MVMThreadContext *tc, MVMStaticFrame *static_frame,
         MVMRegister *env       = static_frame->body.static_env;
         MVMuint8    *flags     = static_frame->body.static_env_flags;
         MVMint64     numlex    = static_frame->body.num_lexicals;
+        MVMCode     *cref      = (MVMCode *)frame->code_ref;
         MVMRegister *state     = NULL;
         MVMint64     state_act = 0; /* 0 = none so far, 1 = first time, 2 = later */
         MVMint64 i;
@@ -577,18 +578,19 @@ void MVM_frame_invoke(MVMThreadContext *tc, MVMStaticFrame *static_frame,
                     redo_state:
                     switch (state_act) {
                     case 0:
-                        if (!frame->code_ref)
+                        if (!cref)
                             MVM_exception_throw_adhoc(tc,
                                 "Frame must have code-ref to have state variables");
-                        state = ((MVMCode *)frame->code_ref)->body.state_vars;
+                        state = cref->body.state_vars;
                         if (state) {
                             /* Already have state vars; pull them from this. */
                             state_act = 2;
                         }
                         else {
                             /* Allocate storage for state vars. */
                             state = (MVMRegister *)MVM_calloc(1, frame->static_info->body.env_size);
-                            ((MVMCode *)frame->code_ref)->body.state_vars = state;
+                            cref->body.state_vars = state;
+                            cref->body.state_vars_is_hll_init = (MVMuint8 *)MVM_calloc(1, numlex);
                             state_act = 1;
 
                             /* Note that this frame should run state init code. */