message_list_view: Extract `_get_msg_timestring` method.
message_list_view: Extract `_get_msg_timestring` method.

This method gets the timestring for the message container when the
message was last edited.

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