builtin: add runtime check for []Type{cap: negative}

[Delta456]

PR similar to #23294 but for cap

_{Huly®: V_0.6-21739}

[JalonSolov]

Separate PR would be fine, but... probably should have a check for init as well, so that

a := []u8{len: 5, init: -1}

is invalid.

a := []u8{len: 5, init: ~0}

would have the same effect, but it is not trying to assign a negative number to an unsigned value.