Use a new Step value for Enter WPCOM email screen

[selanthiraiyan]

Related to - woocommerce/woocommerce-ios#7572 and woocommerce/woocommerce-ios#7573

Changes

GetStartedViewController and SiteAddressViewController were using same Step values (.start)

This makes it impossible to differentiate between those two screens in analytics events.

Meanwhile, WC Android uses "enter_email_address" as Step value for Enter email screen (GetStartedViewController)

This PR introduces a new Step value "enter_email_address" and uses that for GetStartedViewController.

Testing instructions

Follow the instructions from woocommerce/woocommerce-ios#7573 to test this.

[jaclync]

LGTM ✅

start is indeed quite vague. does Android also use a different step value for the site address SiteAddressViewController screen? feel free to keep it as it is so that it doesn't affect existing analytics.

[selanthiraiyan]

does Android also use a different step value for the site address SiteAddressViewController screen? feel free to keep it as it is so that it doesn't affect existing analytics.

No, they use start in Android for this screen. i.e. The events are identical in iOS and Android for SiteAddressViewController screen.