Short aliases for infraction editing

[bast0006]

At the moment, !infr edit last or !infr edit l is the fastest way to amend a previous infraction. Similar to #1170, but more limited in scope. Something like !i e l would be nice, if doable, if not !infr e l or even !iel.

[mbaruh]

Just making aliases to infr and edit will allow it to be extendable to the new append subcommand, so that seems good to me.
At the same time, the new subcommand might alter the way we use infr edit last, so we might want to first limit it to what was said in the previous sentence.

[MarkKoz]

!i e l is doable as it simply requires an alias each on the group command and the subcommand. Also consider !ie using the root_aliases feature I added. last or an infraction ID could be passed as an argument as normal. Something like !iel would require a new command to be defined since l (last) is an argument rather than a subcommand.