Directly use VM iseq query functions instead of going through rb_prof…

…ile_ stuff

Since we now always return an iseq from ddtrace_rb_profile_frames
(it's in the name of the struct element even!), we can directly use the
`rb_iseq_` functions.

Looking at the `rb_profile_` functions what they do is check if they
have an iseq or something else, and when they have an iseq, they call
these functions.

So this allows us to skip the extra tests because we know we have iseqs.

(FYI an "iseq" is an "instruction sequence" -- it's the object that
represents the YARV VM bytecode)

ext/datadog_profiling_native_extension/collectors_stack.c

@@ -34,6 +34,11 @@ static void maybe_add_placeholder_frames_omitted(VALUE thread, sampling_buffer*
 static void record_placeholder_stack_in_native_code(VALUE recorder_instance, sample_values values, sample_labels labels);
 static void maybe_trim_template_random_ids(ddog_CharSlice *name_slice, ddog_CharSlice *filename_slice);
 
+// These two functions are exposed as symbols by the VM but are not in any header.
+// Their signatures actually take a `const rb_iseq_t *iseq` but it gets casted back and forth between VALUE.
+extern VALUE rb_iseq_path(const VALUE);
+extern VALUE rb_iseq_base_label(const VALUE);
+
 void collectors_stack_init(VALUE profiling_module) {
   VALUE collectors_module = rb_define_module_under(profiling_module, "Collectors");
   VALUE collectors_stack_class = rb_define_class_under(collectors_module, "Stack", rb_cObject);
@@ -191,8 +196,8 @@ void sample_thread(
     int line;
 
     if (buffer->stack_buffer[i].is_ruby_frame) {
-      name = rb_profile_frame_base_label(buffer->stack_buffer[i].as.ruby_frame.iseq);
-      filename = rb_profile_frame_path(buffer->stack_buffer[i].as.ruby_frame.iseq);
+      name = rb_iseq_base_label(buffer->stack_buffer[i].as.ruby_frame.iseq);
+      filename = rb_iseq_path(buffer->stack_buffer[i].as.ruby_frame.iseq);
       line = buffer->stack_buffer[i].as.ruby_frame.line;
 
       last_ruby_frame_filename = filename;