Make ruby_global_symbols movable

The `ids` array and `dsymbol_fstr_hash` were pinned because they were
kept alive by rb_vm_register_global_object. This prevented the GC from
moving them even though there were reference updating code.

This commit changes it to be marked movable by marking it as a root object.

Author: peterzhu2118

gc.c

@@ -2650,6 +2650,9 @@ rb_gc_mark_roots(void *objspace, const char **categoryp)
     MARK_CHECKPOINT("machine_context");
     mark_current_machine_context(ec);
 
+    MARK_CHECKPOINT("global_symbols");
+    rb_sym_global_symbols_mark();
+
     MARK_CHECKPOINT("finish");
 
 #undef MARK_CHECKPOINT

internal/symbol.h

@@ -17,6 +17,7 @@
 #endif
 
 /* symbol.c */
+void rb_sym_global_symbols_mark(void);
 VALUE rb_to_symbol_type(VALUE obj);
 VALUE rb_sym_intern(const char *ptr, long len, rb_encoding *enc);
 VALUE rb_sym_intern_ascii(const char *ptr, long len);

symbol.c

@@ -95,17 +95,24 @@ Init_sym(void)
 
     VALUE dsym_fstrs = rb_ident_hash_new();
     symbols->dsymbol_fstr_hash = dsym_fstrs;
-    rb_vm_register_global_object(dsym_fstrs);
     rb_obj_hide(dsym_fstrs);
 
     symbols->str_sym = st_init_table_with_size(&symhash, 1000);
     symbols->ids = rb_ary_hidden_new(0);
-    rb_vm_register_global_object(symbols->ids);
 
     Init_op_tbl();
     Init_id();
 }
 
+void
+rb_sym_global_symbols_mark(void)
+{
+    rb_symbols_t *symbols = &ruby_global_symbols;
+
+    rb_gc_mark_movable(symbols->ids);
+    rb_gc_mark_movable(symbols->dsymbol_fstr_hash);
+}
+
 WARN_UNUSED_RESULT(static VALUE dsymbol_alloc(rb_symbols_t *symbols, const VALUE klass, const VALUE str, rb_encoding *const enc, const ID type));
 WARN_UNUSED_RESULT(static VALUE dsymbol_check(rb_symbols_t *symbols, const VALUE sym));
 WARN_UNUSED_RESULT(static ID lookup_str_id(VALUE str));