Support latest Zig version after build phase separation

[Techatrix]

The Zig build system has been reworked internally in #35428. It's been separated into a "make" process and a "configure" process. ZLS can be updated once the build system protocol has been implemented.

Until this issue has been resolved, it is recommended that users that need ZLS stick to Zig 0.16.0 with ZLS 0.16.0.

[Techatrix]

The current progress can be found in the following branch:
https://github.com/zigtools/zls/tree/techatrix/build-runner-process

This requires a fork of the Zig compiler until the necessary changes have been upstreamed:
https://codeberg.org/Techatrix/zig/src/branch/bsp

The most important features like @import("some_module") and build on save already work in most cases.