Track emoji metrics for a merge request

Task:

Track the following metrics with HLL tracking

Action	Description
reaction_thumbs_up	Added thumbs up reaction to MR
reaction_thumbs_down	Added thumbs down reaction to MR
reaction_added	Added emoji reaction to MR
reaction_removed	Removed emoji reaction to MR
comment_reaction_added	Added emoji reaction to a comment in the MR
comment_reaction_removed	Removed emoji reaction to a comment in the MR