message_list_view: Add highlight for user group mentions.
message_list_view: Add highlight for user group mentions.

Add green highlight to mentions of user groups the current user
is a member of.

Fixes part of #11026.

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