Switch to `termcolor` (first)?

[crlf0710]

There're on going effort to move libtest out of tree, however i think the current approach(#59440) is a little too aggressive by changing everything in a huge PR. I think it the effort should be splitted and happen in several separate steps.

The first big step in it is replacing libterm with termcolor, which means:

• Add separate features to termcolor, wincolor, and winapi to mark these crates unstable (so they can be shipped with rustc.
• Maybe move these crates repo to rust-lang organization.
• Modify libtest in-tree to use termcolor

An alternative is to keep the existing code for unstable rustc usage but make it a shim over termcolor for non-rustc usages.

Just wrote these down to see what peoples think. @alexcrichton @Manishearth @gnzlbg @BurntSushi

[euclio]

I'm working on this. I have local builds of the aforementioned crates that allows completely migrating over to termcolor.

I've opened retep998/winapi-rs#831 as a first step, but it's blocked until winapi can upgrade its MSRV in 0.4.

Also, as mentioned in #63725, we'll need to fix kennytm/fwdansi#1 before upgrading the termcolor version.

[crlf0710]

As an inferior alternative, I have a fork of termcolor at https://github.com/crlf0710/termcolor, where winapi dependency is removed. Feel free to cherry-pick anything that's usefu to you.