Re-add Block Editor e2e test

[cameronvoell]

Previously we had an e2e test for opening the Block Editor and then switching to the classic editor, that test was disabled because of performance constraints.

The Block Editor has had some performance improvements since that test had @Ignore key word added, it may be a good time to revisit adding a simple Block Editor test to the WPAndroid e2e test suite for catching issues related to Gutenberg editor code version mismatches or other issues with the Block Editor.

Relevant file: https://github.com/wordpress-mobile/WordPress-Android/blob/develop/WordPress/src/androidTest/java/org/wordpress/android/e2e/BlockEditorTests.java

[jd-alexander]

@cameronvoell would it be fine to reuse the test that exists here and remove the classic editor related logic in it since it's going to be removed soon? I am going to go ahead and give this a go.