[6.x] Fail contains field conditions against an object instead of throwing

[joshdaugherty]

Fixes #15534

A contains or includes condition on a field whose value is a plain object, such as a date range ({ start, end }) or a group, threw TypeError: condition.lhs.includes is not a function. prepareLhs() passes objects through unchanged so that arrays keep includes(), and passesIncludesCondition() called includes() without checking it exists.

passesIncludesCondition() now fails the condition when the value can't be searched, which matches how passesCondition() already treats an object for every other operator (if (isObject(condition.lhs)) return false). Arrays and strings are unaffected, and under unless the failed condition still inverts as usual.

Tests

Adds it fails includes or contains conditions against an object instead of throwing to resources/js/tests/FieldConditionsValidator.test.js, with a date range and a group-like object under contains, includes and unless. On 6.x without the change it throws TypeError: condition.lhs.includes is not a function; with it, it passes. The file's other 52 tests still pass, and npx vitest run --project unit passes (628 tests).