Select all artifact jobs when testing

[hugovk]

The "build artifacts" workflow can triggered in three ways:

• workflow_dispatch: when make a real release. The actual release Git remote/commit/version are passed in as inputs.
• push and pull_request: when opening PRs to test we've not broken anything. A default remote/commit/version is used.

This is a follow on from #365, which changed the default for testing from 3.14 to 3.15, so we can test the new iOS job. A drawback of this is 3.15 is still in alpha, and so won't select the docs test until RC.

Instead, when we're testing, let's select all jobs, so we test docs, iOS and Android. A bit like a reverse Volkswagen mode :)

Also added summaries to the build pages.

Demos:

push	workflow_dispatch
Select all	Select based on version