Support project-defined zig versions using `build.zig.zon`'s `minimum_zig_version`

[paperclover]

Zig projects with dependencies will have a build.zig.zon

.{
    // ...

    // This field is optional.
    // This is currently advisory only; Zig does not yet do anything
    // with this value.
    .minimum_zig_version = "0.13.0",

    // ...
}

It would be nice to use this as a source for a compiler version.

[paperclover]

Another thing on top of this would be a way to update the zig version, in which it replaces this field.

[trnxdev]

something like zigd update?