Use slices package from the stdlib when possible (#5360)

* Use slices from the stdlib when possible

* Add some unit tests

* More small tweaks + add benchmark func

pkg/sqlite/studio.go

@@ -5,6 +5,7 @@ import (
 	"database/sql"
 	"errors"
 	"fmt"
+	"slices"
 
 	"github.com/doug-martin/goqu/v9"
 	"github.com/doug-martin/goqu/v9/exp"
@@ -13,7 +14,6 @@ import (
 	"gopkg.in/guregu/null.v4/zero"
 
 	"github.com/stashapp/stash/pkg/models"
-	"github.com/stashapp/stash/pkg/sliceutil"
 	"github.com/stashapp/stash/pkg/studio"
 )
 
@@ -305,7 +305,7 @@ func (qb *StudioStore) FindMany(ctx context.Context, ids []int) ([]*models.Studi
 		}
 
 		for _, s := range unsorted {
-			i := sliceutil.Index(ids, s.ID)
+			i := slices.Index(ids, s.ID)
 			ret[i] = s
 		}