Run our full automation test suite on all new changes to the develop branch

[guarani]

Is your feature request related to a problem? Please describe.

We found in the 1.63.0 release that Dependabot caught an incoming Gutenberg breakage after the fact (i.e. after a previous PR had update the Gutenberg submodule ref). Dependabot was able to catch the breakage while the previous PR did not, because Dependabot runs optional tests by default, but regular PRs do not (they are optional tests that must be manually triggered).

Describe the solution you'd like

Dependabot runs daily, so to reduce the amount of time between a breakage being introduced and it potentially being caught by Dependabot, this issue proposes to have all updates to the Gutenberg Mobile develop branch trigger the full suite of tests. I think this is similar to the main apps which run optional tests after PRs have merged to develop (e.g. here for WPiOS, and here for WPAndroid).

Describe alternatives you've considered

Alternatives include:

• making Gutenberg Mobile optional tests not optional anymore (would slow down our workflow for all developers)
• leaving things as-is since this proposal only shortens the time between an incoming Gutenberg breakage being introduced and it being detected, it doesn't avoid detection happening after the fact
• Moving optional tests to the Gutenberg repo and possibly running them there on all updates to trunk (would slow down the workflow for all mobile/web developers)

[guarani]

Dependabot might not be the right tool to achieve the goal of running optional tests on every update to develop, since this task won't involve updating dependencies.

[mchowning]

👍 I like this idea!

[guarani]

👋 Hey @mchowning, I've updated the issue now that I think a solution to this involves CircleCI, not Dependabot. I've also added you as a reviewer here: #4114
We could definitely discuss this as a team before moving ahead with it (since it's a change that affects our shared workflow), but I'm keen to hear what you think at this early stage.