`addTest` and `findProgram` methods of `std.Build` use deprecated `host` field instead of `graph.host`

[Trevor-Strong]

Zig Version

0.12.0

Steps to Reproduce and Observed Behavior

In #19684 the host field was deprecated; however, the addTest and findProgam methods of std.Build still use this field instead of the suggested replacement of graph.host.

Expected Behavior

I would expect the standard library to use the graph.host field instead of the deprecated host field.

I have also checked that these are the only two places under std.Build or the build runner that make this mistake, and that this is present on master at the time of writing.

[andrewrk]

Unobservable internal implementation details are not a bug and do not warrant an issue.

Notice that your "observed behavior" contains no observed behavior.