rename `rb_thread_t::locking_native_thread`

to `rb_thread_t::has_dedicated_nt`

tool/rjit/bindgen.rb

@@ -625,7 +625,7 @@ generator = BindingGenerator.new(
     'RString.as': %w[embed], # doesn't compile on USE_RVARGC=0 CI
     rb_execution_context_struct: %w[method_missing_reason], # non-leading bit fields not supported
     rb_iseq_constant_body: %w[yjit_payload], # conditionally defined
-    rb_thread_struct: %w[status locking_native_thread to_kill abort_on_exception report_on_exception pending_interrupt_queue_checked],
+    rb_thread_struct: %w[status has_dedicated_nt to_kill abort_on_exception report_on_exception pending_interrupt_queue_checked],
     :'' => %w[is_from_method is_lambda is_isolated], # rb_proc_t
   },
   ruby_fields: {

vm_core.h

@@ -1011,7 +1011,7 @@ typedef struct rb_thread_struct {
 
     BITFIELD(enum rb_thread_status, status, 2);
     /* bit flags */
-    unsigned int locking_native_thread : 1;
+    unsigned int has_dedicated_nt : 1;
     unsigned int to_kill : 1;
     unsigned int abort_on_exception: 1;
     unsigned int report_on_exception: 1;