ClangFormat: Replace checks widget with editor

The existing approach utilizing the widget poses maintenance
challenges, primarily due to the dynamic nature of clang-format
settings across versions. The widget necessitates regeneration
for each new version, and compatibility issues arise when users
have different clang-format versions on their devices.

The updated solution adopts an Editor integrated with a yaml
language server, offering the ability to highlight and provide
code completion for the .clang-format file. This resolves the
widget regeneration issue and ensures compatibility with various
clang-format versions.

- Replaced the checks widget with an editor
- Introduced a line for yaml language server schema
in .clang-format files to enable autocompletion.
ToDo: Enhance schema accessibility without relying on this line.
- Added Ctrl+Space shortcut for autocompletion
- Added Ctrl+S shortcut for saving
- Eliminated outdated logic related to the checks widget
- Fixed copying and removal of clang-format settings

Change-Id: I2e3fbf19abe2f4df031f6ba5faffd47e07274346
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>
Reviewed-by: David Schulz <david.schulz@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>

src/plugins/texteditor/textdocument.cpp

@@ -292,6 +292,8 @@ TextDocument *TextDocument::currentTextDocument()
 
 TextDocument *TextDocument::textDocumentForFilePath(const Utils::FilePath &filePath)
 {
+    if (filePath.isEmpty())
+        return nullptr;
     return qobject_cast<TextDocument *>(DocumentModel::documentForFilePath(filePath));
 }