Feature request: parse label and milestone references (~ and %) in issue filter bar

When typing a label or a milestone into the issue or merge request filter bar, it would be really helpful to be able to just start typing ~reg... and then select regression from the dropdown menu, instead of typing out Label: regression. This would allow the filter bar to work similarly to the way we are already used to adding label and milestone references within issue notes.

/cc @ClemMakesApps