refactor: use is_key_* helpers for consistency in key event methods

[gaesa]

Description

This PR refactors as_key_release_event and as_key_repeat_event to use the existing is_key_release and is_key_repeat helper methods for consistency. This aligns all as_key_*_event methods to follow the same structure, improving maintainability.

Changes

• as_key_release_event now calls is_key_release() instead of manually checking event.kind == KeyEventKind::Release
• as_key_repeat_event now calls is_key_repeat() instead of manually checking event.kind == KeyEventKind::Repeat

Rationale

• is_key_press_event already uses is_key_press(), so the other two methods should follow the same pattern.
• The matches! macro used in is_key_* functions is more general and can sometimes be optimized better by the compiler.
• Improves code clarity.

[joshka]

Thanks!