Improved ref switcher dropdown performance

What does this MR do?

Removes jQuery creating elements, instead uses vanilla JS to create elements. This increase the performance significantly, previously with ~500 branches render time was approx. 30ms, with this change it dropped down to approx. 5ms.

The JSON now returns a maximum of 100 branches & 100 tags. The user can then search for more if they require.

What are the relevant issue numbers?

Closes #18202 (closed)

app/assets/javascripts/gl_dropdown.js

@@ -249,7 +249,7 @@
                 _this.fullData = data;
                 _this.parseData(_this.fullData);
                 _this.focusTextInput();
-                if (_this.options.filterable && _this.filter && _this.filter.input) {
+                if (_this.options.filterable && _this.filter && _this.filter.input && _this.filter.input.text() !== '') {
                   return _this.filter.input.trigger('input');
                 }
               };