Add scene/image/gallery popover count buttons for performer/studio/tag cards (#1293)

* Add counts to graphql schema
* Add count resolvers and query refactor
* Add count popover buttons

pkg/gallery/query.go

@@ -0,0 +1,40 @@
+package gallery
+
+import (
+	"strconv"
+
+	"github.com/stashapp/stash/pkg/models"
+)
+
+func CountByPerformerID(r models.GalleryReader, id int) (int, error) {
+	filter := &models.GalleryFilterType{
+		Performers: &models.MultiCriterionInput{
+			Value:    []string{strconv.Itoa(id)},
+			Modifier: models.CriterionModifierIncludes,
+		},
+	}
+
+	return r.QueryCount(filter, nil)
+}
+
+func CountByStudioID(r models.GalleryReader, id int) (int, error) {
+	filter := &models.GalleryFilterType{
+		Studios: &models.MultiCriterionInput{
+			Value:    []string{strconv.Itoa(id)},
+			Modifier: models.CriterionModifierIncludes,
+		},
+	}
+
+	return r.QueryCount(filter, nil)
+}
+
+func CountByTagID(r models.GalleryReader, id int) (int, error) {
+	filter := &models.GalleryFilterType{
+		Tags: &models.MultiCriterionInput{
+			Value:    []string{strconv.Itoa(id)},
+			Modifier: models.CriterionModifierIncludes,
+		},
+	}
+
+	return r.QueryCount(filter, nil)
+}