chore(workflows): add ability to cancel all but latest workflow run

[mikehardy]

Description

Previously, only workflows older then the current workflow were canceled

In very deep queues this means the current instance may not even run until there are future
runs enqueued, and those will not run - and thus will not cancel - the current run, leaving
the queue in a clogged state

Now any time a run instance finally gets off the queue and runs it will check all runs -
including runs queued after the current one - and it will clear all non-current runs including
itself, hopefully unclogging the queue

styfle/cancel-workflow-action#62 is the upstream PR

In the process I removed the github_token as in current versions of the action it is optional, and the one that was specified here is now the default.

Related Issues

No related issue logged, but @Salakar and @rrousselGit mentioned it was hurting productivity and requested I take a look

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Breaking Change

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