test: test various calling patterns of net.connect() related functions

[joyeecheung]

Related: #11761
This PR adds coverage to more calling patterns of net.connect:

• Cover the calling pattern net.connect(), net.createConnection(), new Socket().connect() with/without callback, with port passed in plain argument/in option
• Refactor test-net-create-connection.js and rename it to test-net-connect-options-port.js
• Add tests for connect(path)
• Refactor test-net-connect-options.js, add tests for more new Socket() options.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines

Affected core subsystem(s)

test, net

[joyeecheung]

CI: https://ci.nodejs.org/job/node-test-pull-request/6839/
New CI: https://ci.nodejs.org/job/node-test-pull-request/6841/

[joyeecheung]

Error messages vary on different machines..loosen up the message validation and try again. CI: https://ci.nodejs.org/job/node-test-pull-request/6850/

[joyeecheung]

Something is wrong with net.connect({fd: TCPfd})(keep getting ENOTCONN or flaky libuv assertion failures)..probably has something to do with the state management. I'll remove it from this PR for now and investigate later. Pipe fd works fine though.

@jasnell PTAL, thanks.

CI is green now: https://ci.nodejs.org/job/node-test-pull-request/6867/

[jasnell]

Still LGTM!

[jasnell]

Landed in 7b830f4

[italoacasas]

This PR need backport to v7

[gibfahn]

@joyeecheung Should this be backported to v6.x-staging? If yes please follow the guide and raise a backport PR, if no let me know or add the dont-land-on label.

If it is backported, the PR should include #12601.