feat: Public visibility for resolveRelationColumn method

[Seb33300]

Alternative to #3229

Not sure which implementation is better, I will let you choose what you prefer.

I would like to suggest to make resolveRelationColumn() a public method so we can reuse it in our custom filters:

$datatable = new EloquentDataTable($query);

$datatable
    ->filter(function ($query) use ($datatable) {
        // resolveRelationColumn automatically create joins if needed
        $column = $datatable->resolveRelationColumn('foo.bar');
        $query->where($column, 'xxx');
    })
    ->filterColumn('foo.bar', function ($query, $keyword) use ($datatable) {
        // resolveRelationColumn automatically create joins if needed
        $column = $datatable->resolveRelationColumn('foo.bar');
        $query->where($column, 'xxx');
    })
;

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[Seb33300]

Since #3229 is merged, this on is no longer needed.