message: Extract build_message_send_dict function.
message: Extract build_message_send_dict function.

We extract the loop for building message dict in
do_send_messages in a separate function named
build_message_send_dict.

This is a prep commit for moving the code for building
of message dict in check_message.

kou/zulip,eeshangarg/zulip,showell/zulip,showell/zulip,punchagan/zulip,kou/zulip,zulip/zulip,kou/zulip,zulip/zulip,andersk/zulip,hackerkid/zulip,punchagan/zulip,showell/zulip,zulip/zulip,eeshangarg/zulip,rht/zulip,rht/zulip,showell/zulip,zulip/zulip,andersk/zulip,zulip/zulip,hackerkid/zulip,showell/zulip,rht/zulip,hackerkid/zulip,rht/zulip,zulip/zulip,kou/zulip,andersk/zulip,punchagan/zulip,eeshangarg/zulip,hackerkid/zulip,hackerkid/zulip,zulip/zulip,andersk/zulip,showell/zulip,eeshangarg/zulip,rht/zulip,punchagan/zulip,rht/zulip,eeshangarg/zulip,hackerkid/zulip,hackerkid/zulip,kou/zulip,kou/zulip,kou/zulip,rht/zulip,punchagan/zulip,showell/zulip,eeshangarg/zulip,andersk/zulip,punchagan/zulip,punchagan/zulip,eeshangarg/zulip,andersk/zulip,andersk/zulip