puppeteer: Add common methods needed for 02-messages-basics.js.
puppeteer: Add common methods needed for 02-messages-basics.js.

We include all method needed from casper except
get_rendered_messages, and expected_messages. We will want to tweak
their API when we migrate them.

We also rename bunch of method here while migrating them.

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