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/constexpr_notnull_tests.cpp

@@ -28,15 +28,15 @@ constexpr bool comparison_test(const int* ptr1, const int* ptr2)
     const not_null<const int*> p1(ptr1);
     const not_null<const int*> p1_same(ptr1);
     const not_null<const int*> p2(ptr2);
-    
+
     // Testing operator==
     const bool eq_result = (p1 == p1_same); // Should be true
     const bool neq_result = (p1 != p2);     // Should be true
-    
+
     // Testing operator<= and operator>=
     const bool le_result = (p1 <= p1_same); // Should be true
     const bool ge_result = (p1 >= p1_same); // Should be true
-    
+
     // The exact comparison results will depend on pointer ordering,
     // but we can verify that the basic equality checks work as expected
     return eq_result && neq_result && le_result && ge_result;
@@ -47,11 +47,11 @@ constexpr bool workaround_test(const int* ptr1, const int* ptr2)
     const not_null<const int*> p1(ptr1);
     const not_null<const int*> p1_same(ptr1);
     const not_null<const int*> p2(ptr2);
-    
+
     // Using .get() to compare
     const bool eq_result = (p1.get() == p1_same.get()); // Should be true
     const bool neq_result = (p1.get() != p2.get());     // Should be true
-    
+
     return eq_result && neq_result;
 }
 } // namespace
@@ -59,8 +59,10 @@ constexpr bool workaround_test(const int* ptr1, const int* ptr2)
 constexpr int test_value1 = 1;
 constexpr int test_value2 = 2;
 
-static_assert(comparison_test(&test_value1, &test_value2), "not_null comparison operators should be constexpr");
-static_assert(workaround_test(&test_value1, &test_value2), "not_null .get() comparison workaround should work");
+static_assert(comparison_test(&test_value1, &test_value2),
+              "not_null comparison operators should be constexpr");
+static_assert(workaround_test(&test_value1, &test_value2),
+              "not_null .get() comparison workaround should work");
 
 TEST(notnull_constexpr_tests, TestNotNullConstexprComparison)
 {
@@ -71,4 +73,3 @@ TEST(notnull_constexpr_tests, TestNotNullConstexprComparison)
     EXPECT_TRUE(comparison_test(&value1, &value2));
     EXPECT_TRUE(workaround_test(&value1, &value2));
 }
-