[style] apply IWYU to public headers (#11580)

It would be easier to use OpenThread public headers if they are
self-contained and follows the IWYU style guide. This commit fixes some
style issues to make the public headers self-contained and IWYU. The
existing pretty check is also extended to verify the OpenThread public
headers are self-contained and follows IWYU.

script/bootstrap

@@ -48,6 +48,8 @@ install_packages_pretty_format()
 
     # add shfmt for shell pretty
     command -v shfmt || sudo apt-get install shfmt || echo 'WARNING: could not install shfmt, which is useful if you plan to contribute shell scripts to the OpenThread project.'
+
+    sudo apt-get --no-install-recommends install -y iwyu || echo 'WARNING: iwyu, which is useful to ensure applying the IWYU rules.'
 }
 
 install_packages_apt()
@@ -122,6 +124,8 @@ install_packages_brew()
 
     # add yapf for pretty
     python3 -m pip install yapf || echo 'Failed to install python code formatter yapf. Install it manually if you need.'
+
+    brew install include-what-you-use || echo 'WARNING: iwyu, which is useful to ensure applying the IWYU rules.'
 }
 
 install_packages_source()

script/check-iwyu-public-header

@@ -0,0 +1,44 @@
+#!/bin/bash
+#
+#  Copyright (c) 2025, The OpenThread Authors.
+#  All rights reserved.
+#
+#  Redistribution and use in source and binary forms, with or without
+#  modification, are permitted provided that the following conditions are met:
+#  1. Redistributions of source code must retain the above copyright
+#     notice, this list of conditions and the following disclaimer.
+#  2. Redistributions in binary form must reproduce the above copyright
+#     notice, this list of conditions and the following disclaimer in the
+#     documentation and/or other materials provided with the distribution.
+#  3. Neither the name of the copyright holder nor the
+#     names of its contributors may be used to endorse or promote products
+#     derived from this software without specific prior written permission.
+#
+#  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+#  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+#  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+#  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+#  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+#  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+#  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+#  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+#  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+#  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+#  POSSIBILITY OF SUCH DAMAGE.
+#
+
+#
+# Run this command on parent directory of openthread
+#
+
+set -euxo pipefail
+
+main()
+{
+    find include -name '*.h' -exec iwyu -I include {} \; 2>&1 \
+        | fix_include -n --nosafe_headers \
+        | tee >(cat 1>&2) \
+        | grep 'IWYU edited 0 files on your behalf.'
+}
+
+main "$@"