Normalize MS map_ BIF names and document grammar.

[christhekeele]

Picked up and played with erlang#7326 a little @sverker, here's a PR form of some of my thoughts.

• Renames maps_put and maps_remove to map_put and map_remove

  The reasoning being:

  • The pre-existing map_get call allowed in matchspecs today is singular
  • This is to mirror the auto-imported map_get BIF in the erlang module; in the future if map put/remove BIFs are added to erlang they would be named similarly too
    • I'm playing with this a little, but very out of my depth

• Allows map_put and map_remove in trace matchspec bodies

  • I think we may as well allow modification of maps used in tracing; ex. adding some sort of metadata into a map being used as an emitted message in certain trace patterns

• Separates these functions from action functions in both documentation and implementation

• Updates the matchspec grammar docs