capture: add sysprof_collector_is_active()

This can be used to check if a collector is actively running.

src/libsysprof-capture/sysprof-collector.c

@@ -863,3 +863,15 @@ sysprof_collector_request_counter (unsigned int n_counters)
 
   return ret;
 }
+
+bool
+sysprof_collector_is_active (void)
+{
+  bool ret = false;
+
+  COLLECTOR_BEGIN {
+    ret = true;
+  } COLLECTOR_END;
+
+  return ret;
+}

src/libsysprof-capture/sysprof-collector.h

@@ -65,6 +65,8 @@ SYSPROF_BEGIN_DECLS
 
 SYSPROF_AVAILABLE_IN_3_36
 void         sysprof_collector_init            (void);
+SYSPROF_AVAILABLE_IN_3_38
+bool         sysprof_collector_is_active       (void);
 SYSPROF_AVAILABLE_IN_3_36
 void         sysprof_collector_allocate        (SysprofCaptureAddress             alloc_addr,
                                                 int64_t                           alloc_size,