Support running Drupal 7 tests against SQLite as a "default" rather than "non-standard" environment

Based on my results trying this with patch-level testing on a contrib module (see https://www.drupal.org/node/2762535#comment-11379427), as well as running tests on SQLite locally, it seems like the Drupal core bug at #1713332: The SQLite database driver fails to drop simpletest tables results in a test failure for practically every test that is run in both core and contrib. So turning this on for Drupal 7 probably wouldn't be that useful yet. Postponing until that issue is fixed.

Moved to DrupalCI Environments.

So, any patch as well as any branch can choose to test against sqlite. When d7 core is ready to pass all sqlite tests, we can easily add it as a potential default. There exists a 5.5/5.6/7.0.14 environment for sqlite and you can set this as a non-standard environment.

Yeah, things have changed since this issue was originally filed. It used to be impossible to have regular branch testing (e.g. on commit) on SQLite. Now it's possible, but requires choosing something from the "non-standard" section of the Environment dropdown.

That's still appropriate for now, but as soon as #1713332: The SQLite database driver fails to drop simpletest tables is fixed this issue can be un-postponed. (Doesn't necessarily require other SQLite test failures in Drupal core, if there are any, to be resolved - but as explained above that issue essentially blocks contrib testing too.)

Clarifying title - it's up to individual project maintainers whether they want to actually enable this or not :)

Okay, we deployed a change to the way jobs were being sent so sqlite tests are possible on d7 now: #2842855: DCI_Jobtype should be set by the api version, not configured in the environment settings

DrupalCI wasnt properly building a d7 site with sqlite, and now it is, so work/testing on d7 sqlite is no longer blocked on the infrastructure.

Unpostpone when you want sqlite moved from "non-standard" to "supported"

The 'non-standard' and supported designations no longer exist, thus, nothing to do here.