message-edit: Add press to Enter to Save edited message functionality.
message-edit: Add press to Enter to Save edited message functionality.

This couples the behavior of Enter to Save with Enter to Send.
Extracts and exports functions responsible for checking if enter
does send/edit and handling default behavior otherwise.
Changes made in static/js/message_edit.js and
static/js/composebox_typeahead.js

Fixes #10320.

synicalsyntax/zulip,andersk/zulip,tommyip/zulip,hackerkid/zulip,hackerkid/zulip,showell/zulip,tommyip/zulip,andersk/zulip,andersk/zulip,andersk/zulip,hackerkid/zulip,brainwane/zulip,andersk/zulip,andersk/zulip,tommyip/zulip,synicalsyntax/zulip,rishig/zulip,zulip/zulip,rishig/zulip,eeshangarg/zulip,brainwane/zulip,kou/zulip,kou/zulip,zulip/zulip,punchagan/zulip,dhcrzf/zulip,zulip/zulip,tommyip/zulip,showell/zulip,rht/zulip,rht/zulip,rishig/zulip,eeshangarg/zulip,timabbott/zulip,tommyip/zulip,kou/zulip,timabbott/zulip,shubhamdhama/zulip,rishig/zulip,eeshangarg/zulip,kou/zulip,timabbott/zulip,rishig/zulip,hackerkid/zulip,brainwane/zulip,rishig/zulip,synicalsyntax/zulip,shubhamdhama/zulip,rht/zulip,hackerkid/zulip,shubhamdhama/zulip,timabbott/zulip,rht/zulip,hackerkid/zulip,dhcrzf/zulip,eeshangarg/zulip,punchagan/zulip,showell/zulip,shubhamdhama/zulip,punchagan/zulip,eeshangarg/zulip,brainwane/zulip,dhcrzf/zulip,zulip/zulip,synicalsyntax/zulip,timabbott/zulip,eeshangarg/zulip,zulip/zulip,dhcrzf/zulip,kou/zulip,punchagan/zulip,synicalsyntax/zulip,shubhamdhama/zulip,showell/zulip,shubhamdhama/zulip,punchagan/zulip,andersk/zulip,showell/zulip,dhcrzf/zulip,punchagan/zulip,timabbott/zulip,showell/zulip,tommyip/zulip,showell/zulip,shubhamdhama/zulip,hackerkid/zulip,brainwane/zulip,synicalsyntax/zulip,rishig/zulip,dhcrzf/zulip,zulip/zulip,synicalsyntax/zulip,brainwane/zulip,eeshangarg/zulip,kou/zulip,tommyip/zulip,kou/zulip,timabbott/zulip,rht/zulip,punchagan/zulip,rht/zulip,rht/zulip,dhcrzf/zulip,zulip/zulip,brainwane/zulip