Updated comment reflects driverProvider/sauce.ts using port 443 instead of port 80.

This change updates documentation on the different proxies.

The sauceAgent key's comment said that adding a webDriverProxy would override this and this is not true. sauceAgent is overwritten by sauceProxy since both are passed onto the saucelabs module.

This means that if you are under a corporate proxy and need to proxy both Sauce Labs API calls as well as calls to the Selenium endpoint (ondemand.saucelabs.com) both sauceProxy/sauceAgent and webDriverProxy need to be used.

This change allows user to define the backend region from sauce via the `sauceRegion` property, e.g. 

```js
    sauceUser: process.env.SAUCE_USERNAME,
    sauceKey: process.env.SAUCE_ACCESS_KEY,
    sauceRegion: 'eu',
```

Will run the test against `https://ondemand.eu-central-1.saucelabs.com:443/wd/hub/.`

```js
    sauceUser: process.env.SAUCE_USERNAME,
    sauceKey: process.env.SAUCE_ACCESS_KEY,
    sauceRegion: 'us',

    // the default
    sauceUser: process.env.SAUCE_USERNAME,
    sauceKey: process.env.SAUCE_ACCESS_KEY,
```

Will run the test against https://ondemand.saucelabs.com:443/wd/hub/

Node v10

We can't upgrade the version of Selenium without transitioning off the
control flow and breaking a bunch of people. Chrome v75 introduced the
new W3C actions API. Unfortunately, we can't update to support that
API without introducing other breakages, so v74 is the last version
of Chrome that will work with Protractor 5.

You can download a Chrome v74 snapshot from https://commondatastorage.googleapis.com/chromium-browser-snapshots/Linux_x64/638880/chrome-linux.zip

You might also need to pass "--no-sandbox" flag to Chrome

Doing this automatically means we can't pin the version of webdriver
that we use in CI. Instead, we run update in the circle config.

…oxy to 4.5.4

travis_wait is not needed if the sauce connect proxy logs are written to
stdout. This makes debugging proxy problems from the CI logs much
easier. This commit also updates the debugging command to use the
`--doctor` flag.

Other changes include:
1. Upgrade sauce-connect proxy from 4.4.1 to 4.5.4

Optimist has been deprecated over 2 years ago as has a security vulnerability. With this change we use it's successor `yargs`.

Closes: #5413