fs: Add Kernel-level VFS Performance Profiler

This adds a kernel-level performance profiler for the VFS.
By enabling CONFIG_FS_PROFILER, the core VFS system calls
(file_read, file_write, file_open, and file_close) are
instrumented to track high-resolution execution times using
clock_systime_timespec() seamlessly.

The collected statistics are exposed dynamically via a new
procfs node at /proc/fs/profile, allowing CI regression
testing without needing external debugging tools.

Signed-off-by: Sumit6307 <sumitkesar6307@gmail.com>

Documentation/components/filesystem/index.rst

@@ -543,6 +543,7 @@ NuttX provides support for a variety of file systems out of the box.
   nxffs.rst
   partition.rst
   procfs.rst
+  profiler.rst
   romfs.rst
   rpmsgfs.rst
   smartfs.rst

Documentation/components/filesystem/profiler.rst

@@ -0,0 +1,38 @@
+==============================
+VFS Performance Profiler
+==============================
+
+The Virtual File System (VFS) Performance Profiler provides a simple, in-kernel 
+mechanism to track execution times and invocation counts for core VFS operations 
+(read, write, open, close) seamlessly. This is highly suitable for 
+CI/CD automated regression testing and performance bottleneck identification.
+
+Configuration
+=============
+
+To enable the profiler, select ``CONFIG_FS_PROFILER`` in your Kconfig.
+To expose the metrics dynamically via procfs, ensure ``CONFIG_FS_PROCFS`` is enabled, and 
+the profiler node is included via ``CONFIG_FS_PROCFS_PROFILER``.
+
+Usage
+=====
+
+When enabled, the profiler automatically intercepts calls to the underlying 
+inode operations and records the execution elapsed times using ``perf_gettime()``.
+Since no blocking mutexes are used during updates (fast ``atomic.h`` operations 
+are utilized instead), the overhead is extremely minimal and safely scales on SMP.
+
+To view the current statistics collectively from the NuttShell (NSH), simply 
+read the node:
+
+.. code-block:: bash
+
+    nsh> cat /proc/fs/profile
+    VFS Performance Profile:
+      Reads:          12 (Total time: 4500120 ns)
+      Writes:          3 (Total time:   95050 ns)
+      Opens:          15 (Total time: 1005000 ns)
+      Closes:         15 (Total time:   45000 ns)
+
+The reported times are in the raw ticks/units provided by ``perf_gettime()`` on 
+your specific architecture.