fix(Code Block):Code Block formatting applies to unintended adjacent lines

[Jynx2004]

This pull request updates the formatCode function in formatCode.ts to improve the handling of code block insertion for non-collapsed selections. The changes modify the else condition to achieve the following:

New Behavior: When a non-collapsed selection is detected, the function now:
Creates a new code node.
Inserts the code node as a sibling immediately below the selected node (using anchorNode.insertAfter(codeNode)).
Moves the selected text content into the new code node.
Removes the original selected content.

Rationale: This ensures the code block is placed directly after the selected element in the editor's node structure, maintaining a cleaner and more intuitive document hierarchy compared to the previous approach.

Impact: The change improves the user experience by correctly positioning code blocks relative to the selection, avoiding nested or misplaced nodes.

Closes #7691

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[etrepum]

This PR needs tests to demonstrate that it works. You should also test that it works when multiple lines are selected.

I can confirm that it doesn't work correctly when two lines separated by a linebreak are selected and then converted to a code block.

[Jynx2004]

This PR needs tests to demonstrate that it works. You should also test that it works when multiple lines are selected.

I can confirm that it doesn't work correctly when two lines separated by a linebreak are selected and then converted to a code block.

Sure will do the testing considering all the cases