Update to zig 0.12.0-dev.1253+b798aaf49

[edyu]

Small changes to prepare for zig 0.12.0

[edyu]

No longer tiny changes, more and more stuff are being renamed but so far "small" changes.

[danmack]

thanks for doing this @ed. I just tested your changes against zig version:
0.12.0-dev.1502+b3462b7ce

and I can confirm that that this now works:

% zig build run-hello
Listening on 0.0.0.0:3000

so works for me but I guess we have to be concerned to keep it working for 0.11 and 0.12 in the meantime.

[renerocksai]

Thanks, Ed. Your changes made it into the new zig-0.12.0 branch!