Add File.getOrEnableAnsiEscapeSupport and use it

[squeek502]

On Windows, the console mode flag ENABLE_VIRTUAL_TERMINAL_PROCESSING determines whether or not ANSI escape codes are parsed/acted on. On the newer Windows Terminal, this flag is set by default, but on the older Windows Console, it is not set by default, but can be enabled (since Windows 10 RS1 from June 2016).

The new File.getOrEnableAnsiEscapeSupport function will get the current status of ANSI escape code support, but will also attempt to enable ENABLE_VIRTUAL_TERMINAL_PROCESSING on Windows if necessary which will provide better/more consistent results for things like std.Progress and std.io.tty.

This type of change was not done previously due to a mistaken assumption (on my part) that the console mode would persist after the run of a program. However, it turns out that the console mode is always reset to the default for each program run in a console session.

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EDIT: A caveat here is that child processes can affect the console mode of parent processes, see #16526 (comment) for an example of how this can cause problems. So this may not actually be fully safe to do, as spawning Zig as a child process can end up messing with the console mode of other processes unexpectedly.

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This is a revivial of #18692 / #15206 (the first commit is cherry-picked from #18692).

Notes:

• See lib/std/fs/File: enable VT seq support for Windows Console #18692 for a nice writeup about ENABLE_VIRTUAL_TERMINAL_PROCESSING
• Console modes are per-screen-buffer, meaning if stderr and stdout share the same screen buffer (usually the case AFAIK), then setting ENABLE_VIRTUAL_TERMINAL_PROCESSING for one will set it for both
• This could allow for dropping support for the Windows console API in std.Progress/std.io.tty, but that is not done in this PR (see rework std.Progress #20059 (comment)). Doing so would mean that color support/progress support would require Windows 10 >= RS1 (from June 2016)

[andrewrk]

Thanks!