libc/stdio: fix freopen fd handling and add fdsan support

[GUIDINGLI]

Summary

This PR fixes the freopen() implementation:

1. Close old fd before reopening: The previous implementation opened the new file first, then used dup2() to replace the old fd. This approach has issues:

   • The old fd remains open until dup2() closes it implicitly
   • Race condition: another thread could use the old fd between open() and dup2()

   The new implementation closes the old fd first, then opens the new file. This allows the kernel to reuse the same fd number, avoiding the need for dup2().

2. Add fdsan support: When CONFIG_FDSAN is enabled, properly handle fd ownership tags:

   • Use android_fdsan_close_with_tag() to close the old fd with correct ownership
   • Use android_fdsan_exchange_owner_tag() to set ownership on the new fd

Impact

• Fixes potential fd leak and race condition in freopen()
• Enables fdsan to correctly track fd ownership through freopen() calls
• No changes to the public API

Testing

• Verified freopen() works correctly with and without CONFIG_FDSAN
• fdsan no longer reports ownership errors when using freopen()
• testcase: test_nuttx_fs_stream01

[acassis]

@GUIDINGLI could you please provide a test example that exercise this issue? Maybe this test should be included in our ostest or NUT test

[GUIDINGLI]

@GUIDINGLI could you please provide a test example that exercise this issue? Maybe this test should be included in our ostest or NUT test

[<0x60ddce>] __assert+0x1d/0x5c
[<0x60f2be>] android_fdsan_exchange_owner_tag+0x71/0xc0
[<0x60a14e>] close+0x19/0x64
[<0xb77b1c>] freopen+0x47/0xd8
[<0x86fe54>] test_nuttx_fs_stream01+0x4f/0x1a4
[<0xcef54e>] cmocka_run_one_test_or_fixture+0xe5/0x3cc
[<0xcefd26>] _cmocka_run_group_tests+0x41d/0xbd8
[<0x86cff2>] cmocka_fs_test_main+0x35/0x58
[<0x6a9d1a>] nxtask_startup+0x15/0x30
[<0x641e92>] nxtask_start+0x75/0x94

That say case is here test_nuttx_fs_stream01