clang-format improvements (#1251)

* clang-format improvements

- Add a clang-format linter check to the PR pipeline
- Apply clang-format to files where the linter initially failed
- Remove `CommentPragmas` from `.clang-format`
- Remove all `// clang-format off` and `// NO-FORMAT` as they are not needed
- Remove a commented out `GSL_SUPPRESS`

* clang-format 20

* pipeline fail

* Update .github/workflows/clang-format.yml

Co-authored-by: Carson Radtke <nosrac925@gmail.com>

* output used clang-format version

* installed version is 18 which replaces "GSL_SUPPRESS(bounds.1)" with "GSL_SUPPRESS(bounds .1)"

* only include/gsl, not include

to prevent formatting of include/CMakeLists.txt

* apply clang-format[-20]

In a VS2026 developer command prompt I ran `clang-format -i include\gsl\* --assume-filename x.cpp`. This was necessary because VS GUI does not format files without an extension :(. Please note that `--assume-filename` is necessary here, otherwise the files will not be formatted. Surprisingly the behaviour for the formatter differs from the behaviour of `lang-format(-20) --dry-run --Werror include/gsl/*` where clang-format recognizes that the files is C++.

* change "#if 0" back to original version with comments only

* formatting scripts for windows and linux

for linux with linter (shfmt and shellcheck)

* add WhitespaceSensitiveMacros: [GSL_SUPPRESS]

* provide path for clang-format (Windows)

Currently not clear to me:
On my personal computer at home, when I start "Developer Command Prompt for VS18", I can run `clang-format` without providing the path.
On my managed (domain) company computer, when I start "Developer Command Prompt for VS18", I can NOT run `clang-format` without providing the path. I need to call `"%VCINSTALLDIR%Tools\Llvm\bin\clang-format"`.
I have no idea what the difference is. At least the version `"%VCINSTALLDIR%Tools\Llvm\bin\clang-format"` works on both computers, so I add the path.

---------

Co-authored-by: Werner Henze <w.henze@avm.de>
Co-authored-by: Carson Radtke <nosrac925@gmail.com>
Co-authored-by: Werner Henze <werner.henze+gitcommits@posteo.de>

tests/at_tests.cpp

@@ -32,7 +32,7 @@
 TEST(at_tests, static_array)
 {
     int a[4] = {1, 2, 3, 4};
-    const int(&c_a)[4] = a;
+    const int (&c_a)[4] = a;
 
     for (int i = 0; i < 4; ++i)
     {
@@ -152,7 +152,7 @@ TEST(at_tests, std_span)
 static constexpr bool test_constexpr()
 {
     int a1[4] = {1, 2, 3, 4};
-    const int(&c_a1)[4] = a1;
+    const int (&c_a1)[4] = a1;
     std::array<int, 4> a2 = {1, 2, 3, 4};
     const std::array<int, 4>& c_a2 = a2;