feat(esp_trace): add compiler-instrumented function tracing support

examples/system/function_tracing/components/ft_demo/include/ft_demo.h

@@ -0,0 +1,34 @@
+/*
+ * SPDX-FileCopyrightText: 2026 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Function Tracing Example - demo library
+*/
+#pragma once
+
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Runs a small nested call graph (ft_demo_run -> level1 -> level2). These
+ * functions are instrumented and appear as function_enter/function_exit. */
+void ft_demo_run(uint32_t iteration);
+
+/* Instrumented file, but excluded by name through the component's
+ * -finstrument-functions-exclude-function-list flag: it produces no events. */
+void ft_demo_secret(void);
+
+/* Lives in ft_demo_hot.c, which is excluded as a whole through the component's
+ * -finstrument-functions-exclude-file-list flag: it produces no events. */
+uint32_t ft_demo_hot_loop(uint32_t n);
+
+/* Lives in ft_demo_quiet.c, a second comma-separated entry in the component's
+ * -finstrument-functions-exclude-file-list flag: it also produces no events. */
+uint32_t ft_demo_quiet_path(uint32_t n);
+
+#ifdef __cplusplus
+}
+#endif