Add autocomplete function to "labels" field in macros like "Recently Updated"

Issue Summary

Autocomplete does not work when selecting a label in the properties of macros like "Recently Updated" macro. when user starts typing in the label field, nothing is populated/suggested which makes it difficult to guess the exact name of the available labels.

Steps to Reproduce

1. Edit a page and insert "Recently Updated" macro
2. Edit the properties of the macro
3. Try to add labels in "Label(s)" field

Expected Results

Autocomplete should start populating the available labels as user is typing

Actual Results

When user starts typing in the label field, nothing is populated/suggested

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available