refactor(examples): group trace examples under examples/system/tracing/

Move 7 trace-related examples (app_trace_basic, app_trace_to_plot,
esp_trace_custom_library, function_tracing, gcov, sysview_tracing,
sysview_tracing_heap_log) from examples/system/ into a dedicated
examples/system/tracing/ subdirectory for better organization.

Update all path references across documentation (en + zh_CN),
build-test-rules, CI configs, Kconfig, and component READMEs.

examples/system/tracing/gcov/components/sample/CMakeLists.txt

@@ -0,0 +1,6 @@
+idf_component_register(SRCS "some_funcs.c"
+                    INCLUDE_DIRS ".")
+
+set_source_files_properties(some_funcs.c
+    PROPERTIES COMPILE_FLAGS
+    --coverage)

examples/system/tracing/gcov/components/sample/some_funcs.c

@@ -0,0 +1,14 @@
+/*
+ * SPDX-FileCopyrightText: 2026 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Unlicense OR CC0-1.0
+ */
+#include <stdio.h>
+
+
+void some_dummy_func(void)
+{
+    static int i;
+    printf("some_dummy_func: Counter = %d\n", i++);
+    i++;
+}