[6.x] Implement whereStatus() on search query builder

[ryanmitchell]

This PR adds whereStatus(string $status) to src/Search/QueryBuilder.php, which calls $this->where('status', $status). This works because:

1. The IteratorBuilder's filterWhereBasic() calls ResolveValue on each result
2. ResolveValue detects that Result implements ContainsQueryableValues and calls getQueryableValue('status')
3. Result::getQueryableValue('status') (already implemented at Result.php:90) calls $this->searchable->status()

Closes #11751