std.os.windows: add SetConsoleMode

[expikr]

This is crucial for enabling ANSI escape sequences on Windows. If Zig is not going to enable it by default, at least make the sys calls easily available for the boilerplate init procedure:

test {
conststd=@import("std")
constkernel32=std.os.windows.kernel32;
varstdout_mode: u32=undefined;
_=kernel32.GetConsoleMode(std.io.getStdOut().handle, &stdout_mode);
_=kernel32.SetConsoleMode(std.io.getStdOut().handle, stdout_mode|4);
std.debug.print("\n\x1b[30;47m"++"That's all,"++"\x1b[m"++" folks\n", .{});
}

Whereas before, without this change you'd need to do:

test {
conststd=@import("std");
constkernel32=opaque {
usingnamespacestd.os.windows.kernel32;
extern"kernel32"fnSetConsoleMode(*anyopaque,u32) callconv(std.os.windows.WINAPI) c_int;
};
varstdout_mode: u32=undefined;
_=kernel32.GetConsoleMode(std.io.getStdOut().handle, &stdout_mode);
_=kernel32.SetConsoleMode(std.io.getStdOut().handle, stdout_mode|4);
std.debug.print("\n\x1b[30;47m"++"That's all,"++"\x1b[m"++" folks\n", .{});
}

[Vexu]

Previously rejected in #15039