Use x/term on Unix systems, deduplicate tscreen_*.go

[niten94]

Reasons why syscall.Syscall6(syscall.SYS_IOCTL, ...) has to be replaced are written below:

• Syscall(...) and Go 1.23 or newer has to be used with SYS_IOCTL since syscall(2) is removed in OpenBSD 7.5
• unsafe.Pointer has to be converted to uintptr in arguments like written in 4th pattern in documentation

There may be changes in any platform where using syscall.Syscall* will not work, so calls are replaced with functions in x/sys and x/term instead.

Micro started up properly when I tested using an OpenIndiana and OpenBSD 7.6 VM. I do not have a MacOS machine so I cannot test if there are no bugs on MacOS. The changes may not be tested and thought well enough.

Fixes zyedidia/micro#3557

[JoeKar]

Unfortunately I've no MacOS for tests too.

[niten94]

I have split the changes into different commits since not all are similar.

Unfortunately I've no MacOS for tests too.

Would it be possible if Zachary could test if bugs don't occur when running shell commands in Micro with this pull request, and if they do on the commit before e701458 (1482264)?

I remember seeing old comments in issues where he seemed to have MacOS, but I'll re-add tscreen_darwin.go or use poller in tscreen_unix.go if no one could test or bugs are introduced.

[niten94]

Sorry, I realized that there were files I did not add so I added them now.

[niten94]

I realized that it isn't easy to modify the fork to use the same workaround on Mac OS as upstream, even if someone can test. I should have realized this months ago and submitted the current changes while tscreen_darwin.go is retained as a duplicate file, but I have readded the file now.

It's also not much needed to remove small amount of duplicated code, and the workaround on Mac OS doesn't need to be changed for now since there seems to be no bugs reported.