Optimise chat filtering in `draw_chat_message`

[num0005]

• Don't create a new regex for each string.
• Don't convert to utf8 for filtering to then convert right back to utf16 PS: The function feels misnamed, does it actually draw the chat message or does it just push it into some buffer and other code draws it? It's not clear.

[num0005]

seems to work fine

[SnowyMouse]

Ooh, this is pretty nice. Thanks!