[13.x] Fix doesnt_contain validation rule ignoring non-string values - #61493

#61318 switched doesnt_contain to a strict in_array() comparison, but rule parameters always arrive as strings while the validated array can hold integers, floats or booleans. doesnt_contain:1 therefore passes for ['flags' => [1]] and lets the prohibited value through, and the same input can satisfy contains:1 and doesnt_contain:1 at the same time.

This casts the scalar values to string before the strict comparison, the same way #61146 did for the in rule. Exact string matches and the 0e123 bypass that #61318 closed both keep their current behavior.

Fixes #61491.