GH-43796: [C++] Indent preprocessor directives (#43798)

### Rationale for this change

This is for easy to read.

FYI: Google C++ style guide doesn't require indent in preprocessor directives nor deny it:

https://google.github.io/styleguide/cppguide.html#Preprocessor_Directives

```cpp
// Good - directives at beginning of line
  if (lopsided_score) {
#if DISASTER_PENDING      // Correct -- Starts at beginning of line
    DropEverything();
# if NOTIFY               // OK but not required -- Spaces after #
    NotifyClient();
# endif
#endif
    BackToNormal();
  }
```

### What changes are included in this PR?

* Add clang-format configurations for preprocessor directives indentation
* Apply these configurations

### Are these changes tested?

Yes.

### Are there any user-facing changes?

No.
* GitHub Issue: #43796

Authored-by: Sutou Kouhei <kou@clear-code.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>