[clang-format] Don't break block comments when sorting includes.

Fixes https://github.com/llvm/llvm-project/issues/34626.

Before, the include sorter would break the code:
```
#include <stdio.h>
#include <stdint.h> /* long
                       comment */
```
and change it into:
```
#include <stdint.h> /* long
#include <stdio.h>
                       comment */
```

This commit handles only the most basic case of a single block comment on an include line, but does not try to handle all the possible edge cases with multiple comments.

Reviewed By: HazardyKnusperkeks

Differential Revision: https://reviews.llvm.org/D118627