chore!: change to use v3 of Tcell

[joelim-work]

• Closes Migrating to Tcell v3 #2284

Changes:

• Use the new v3 of Tcell (from v2).
• Support for SGR 8 (concealed text) is removed as Tcell has dropped support for it. This is a breaking change, however it is a very niche feature and I don't think users are interested in it anyway.
• Map <backspace2> keybindings to <backspace>, since Tcell does this internally. This is a breaking change, however it should be a welcome one as it unifies <backspace> and <backspace2>, which reduces confusion.
• ui.keyAcc and ui.keyCount are changed from []rune to string, since key events in Tcell now store a string instead of a rune. This makes the code easier to work with.
• Utility functions are added for converting between Tcell key events and their string representations (e.g. <space>/<c-a>).
• The key event handling code has largely been rewritten to make the logic clearer.
• Replace SetContent calls with PutStrStyled, this requires rewriting the win.print function to accommodate for the new API.

Anyway I will plan to leave this PR open for a while, and only merge it when it (and the new version of Tcell) becomes more stable.

Warning

Apparently keybindings for capital letters (e.g. G for bottom) don't work in v3 of Tcell. at least for me. I have raised an issue about it.
Fixed now, but I still plan to leave this PR open for a while regardless, not in a rush to merge.

[CatsDeservePets]

Uppercase letters get reported incorrectly for me as well.
I haven't encountered any other bug so far.

On a side note: I've noticed you've been using conventional commits more often lately. I try to align my commit messages to match the repos style. If you plan to stick with them going forward, I will use them as well.

[gdamore]

I fixed the upper case keys issue. Sorry about that!

[joelim-work]

On a side note: I've noticed you've been using conventional commits more often lately. I try to align my commit messages to match the repos style. If you plan to stick with them going forward, I will use them as well.

Yes, it's something I have decided to adopt from now on, since many other projects are using it too. I am uncertain about actually enforcing it though (e.g. via CI), or using it as a replacement for the existing breaking/new/fix labels. Just having some visual structure to the commit history is enough for me.

[CatsDeservePets]

On a side note: I've noticed you've been using conventional commits more often lately. I try to align my commit messages to match the repos style. If you plan to stick with them going forward, I will use them as well.

Yes, it's something I have decided to adopt from now on, since many other projects are using it too. I am uncertain about actually enforcing it though (e.g. via CI), or using it as a replacement for the existing breaking/new/fix labels. Just having some visual structure to the commit history is enough for me.

Cool, I am all for unification. I have been using them myself in privat projects (although I am using the Angular guidelines which famously dropped chore).

I guess using it for commit messages is good for now, we can always expand on that later.