Fixed: Implement colon separated CSI parameters

[fornwall]

Colon separated escape sequences for setting colors

It seems that more and more terminal emulators and terminal programs supports colon (:) as well as semicolon (;) to specify colors:

red=255 green=100 blue=0 
printf "\x1b[38;2;${red};${green};${blue}m TRUECOLOR\n" # Semicolon separated, works in Termux
printf "\x1b[38:2:${red}:${green}:${blue}m TRUECOLOR\n" # Colon separated, implemented in this PR

See https://github.com/termstandard/colors?tab=readme-ov-file#truecolor-support-in-output-devices, where it can be seen that multiple terminal emulators also support using a colon as delimiter nowadays:

• alacritty [delimiter: colon, semicolon] - written in Rust
• iTerm2 [delimiter: colon, semicolon] - since v3 version
• kitty [delimiter: colon,semicolon] - uses OpenGL
• konsole [delimiter: colon, semicolon] - https://bugs.kde.org/show_bug.cgi?id=107487
• xterm - (from 331 (change 330j)
• All libvte based terminals (since 0.36 version) [delimiter: colon, semicolon]
  [..]

This is now implemented in Termux as well. Fixes termux/termux-packages#20655, escape sequence issues with vtm.

See alacritty/vte#22 for a discussion when this was implemented in alacritty/vte.

Colored and styled underlines parsing

We also here start to parse Colored and styled underlines as initially proposed by Kitty:

To set the underline style:

[4:0m # no underline
[4:1m # straight underline
[4:2m # double underline
[4:3m # curly underline
[4:4m # dotted underline
[4:5m # dashed underline
[4m # straight underline (for backwards compat)
[24m # no underline (for backwards compat)

To set the underline color (this is reserved and as far as I can tell not actually used for anything):

[58...m
This works exactly like the codes 38, 48 that are used to set foreground and background color respectively.

To reset the underline color (also previously reserved and unused):
[59m

In this initial step we currently don't support straight/double/curly/dotted/dashed nor colored underlines, but parse them and map them to normal underlines. Fixes termux/termux-packages#20620, escape sequences showing up at the start of neovim. Future follow up work is actually respecting them when rendering, which is (at least IMHO) a nice touch when using code editors with support for it such as neovim.