exercises(queen-attack): consider removing test for negative row/col, and support `u3` fields

[ee7]

The valid range for row and col is from 0-7 inclusive, so it doesn't spark joy to test negative inputs, require input validation, and require the init method to take signed integer parameters.

Follow-up to:

• https://github.com/exercism/zig/commit/b7cd99f3db9457a2b8c14b84f70ed99b55191e06
• https://github.com/exercism/zig/commit/de5aff6c33e696116e65e67809ef0e7c299abe7d
• https://github.com/exercism/zig/commit/290e7f31ea8a521752885c94c4e771398191dfae