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/strict_notnull_tests.cpp

@@ -41,24 +41,16 @@ struct RefCounted
 
 namespace
 {
-// clang-format off
-GSL_SUPPRESS(f.4) // NO-FORMAT: attribute
-// clang-format on
+GSL_SUPPRESS(f.4)
 bool helper(not_null<int*> p) { return *p == 12; }
 
-// clang-format off
-GSL_SUPPRESS(f.4) // NO-FORMAT: attribute
-// clang-format on
+GSL_SUPPRESS(f.4)
 bool helper_const(not_null<const int*> p) { return *p == 12; }
 
-// clang-format off
-GSL_SUPPRESS(f.4) // NO-FORMAT: attribute
-// clang-format on
+GSL_SUPPRESS(f.4)
 bool strict_helper(strict_not_null<int*> p) { return *p == 12; }
 
-// clang-format off
-GSL_SUPPRESS(f.4) // NO-FORMAT: attribute
-// clang-format on
+GSL_SUPPRESS(f.4)
 bool strict_helper_const(strict_not_null<const int*> p) { return *p == 12; }
 
 int* return_pointer() { return nullptr; }
@@ -195,7 +187,6 @@ template <typename U>
 static constexpr bool
     StrictHelperCompilesFor<U, void_t<decltype(strict_helper(std::declval<U>()))>> = true;
 
-
 template <typename U, typename = void>
 static constexpr bool StrictHelperConstCompilesFor = false;
 template <typename U>
@@ -203,7 +194,6 @@ static constexpr bool
     StrictHelperConstCompilesFor<U, void_t<decltype(strict_helper_const(std::declval<U>()))>> =
         true;
 
-
 template <typename U, typename = void>
 static constexpr bool HelperCompilesFor = false;
 template <typename U>
@@ -219,13 +209,12 @@ TEST(strict_notnull_tests, TestStrictNotNull)
         strict_not_null<int*> snn = &x;
 #endif
         static_assert(!StrictHelperCompilesFor<int*>, "!StrictHelperCompilesFor<int*>");
-        static_assert(!StrictHelperConstCompilesFor<int*>,
-                      "!StrictHelperCompilesFor<int*>");
+        static_assert(!StrictHelperConstCompilesFor<int*>, "!StrictHelperCompilesFor<int*>");
 
         const strict_not_null<int*> snn1{&x};
 
         static_assert(StrictHelperCompilesFor<const strict_not_null<int*>>,
-                          "StrictHelperCompilesFor<const strict_not_null<int*>>");
+                      "StrictHelperCompilesFor<const strict_not_null<int*>>");
         helper(snn1);
         helper_const(snn1);