### Preflight Checklist

- [X] I have read the [Contributing Guidelines](https://github.com/electron/electron/blob/main/CONTRIBUTING.md) for this project.
- [X] I agree to follow the [Code of Conduct](https://github.com/electron/electron/blob/main/CODE_OF_CONDUCT.md) that this project adheres to.
- [X] I have searched the [issue tracker](https://www.github.com/electron/electron/issues) for a bug report that matches the one I want to file, without success.

### Electron Version

18.0.4

### What operating system are you using?

Ubuntu

### Operating System Version

Ubuntu 20.0.4

### What arch are you using?

x64

### Last Known Working Electron version

_No response_

### Expected Behavior

File Selection Dialog should show files with the filtered extension, with no need for case match.

### Example:

`*.Foo` files should show up if we set filters for `[{name: 'Foo Files', extensions: ['Foo']}]` or even ``[{name: 'Foo Files', extensions: ['foo']}]`.

### Actual Behavior

File Selection Dialog does not show any files if the Filter contains a mixed case extension string.

### Example:

`*.Foo` files do not show up if we set filters for `[{name: 'Foo Files', extensions: ['Foo']}]` or even ``[{name: 'Foo Files', extensions: ['foo']}]` and any case match setup.

### Testcase Gist URL

https://gist.github.com/047baebf59014c18491c4efdfb75a5f8

### Additional Information

The issue probably come from this [function](https://github.com/electron/electron/blob/main/shell/browser/ui/file_dialog_gtk.cc#L250-L266)  (https://github.com/electron/electron/blob/main/shell/browser/ui/file_dialog_gtk.cc#L250-L266)  that seems to only check for lowercased or uppercased extensions. 

### Example:

`[{name: 'Foo Files', extensions: ['Foo']}]` will only show `*.foo` or `*.FOO` files.

### Gist
In the provided gist, it will ask you to add a `aim-file.Js` file. Please add it. Then run the fiddle. It will open a File Selection Dialog and will not show the `aim-file.Js`. If you change the file type to `All`, that file will show up.
shell/browser/ui/file_dialog_gtk.cc
delete this;
}
void FileChooserDialog::AddFilters(const Filters& filters) {
  for (const auto& filter : filters) {
    GtkFileFilter* gtk_filter = gtk_file_filter_new();
    for (const auto& extension : filter.second) {
      
      std::string file_extension = base::ToLowerASCII("*." + extension);
      gtk_file_filter_add_pattern(gtk_filter, file_extension.c_str());
      
      file_extension = base::ToUpperASCII("*." + extension);
      gtk_file_filter_add_pattern(gtk_filter, file_extension.c_str());
    }
    gtk_file_filter_set_name(gtk_filter, filter.first.c_str());
    gtk_file_chooser_add_filter(dialog_, gtk_filter);
  }
}
bool CanPreview(const struct stat& st) {
  
  
  if (!S_ISREG(st.st_mode)) {
    return false;
  }
  
  
  
  constexpr off_t ArbitraryMax = 100000000ULL;
  return st.st_size < ArbitraryMax;
}
void FileChooserDialog::OnUpdatePreview(GtkFileChooser* chooser) {