QA: refactor VE editing

Using the type_into method in this way causes a couple of issues:

* one is that it is only used once and so no need to abstract it
* another is that having steps before expectations breaks the
Given/When/Then intended to be used. This is also the source
of the stale elements noted below.
* because of how the page is (re)used, Selenium sometimes encounters
stale elements [1]
* and sending a space to VE fixes a Selenium-Firefox problem [2]

[1] https://integration.wikimedia.org/ci/view/BrowserTests/view/-All/job/browsertests-MobileFrontend-en.m.wikipedia.beta.wmflabs.org-linux-chrome-sauce/207/testReport/junit/(root)/VisualEditor%20Mobile/I_can_edit_a_page_using_VisualEditor/

[2] https://integration.wikimedia.org/ci/view/BrowserTests/view/-All/job/browsertests-MobileFrontend-en.m.wikipedia.beta.wmflabs.org-linux-firefox-sauce/243/testReport/(root)/VisualEditor%20Mobile/I_can_edit_a_page_using_VisualEditor/

Change-Id: I3294e5a35873d6bd528dd8bd5df04d35c3b1070c
Merge "QA: refactor VE editing"