[ML] Make it easier to delete a failed transform

[sophiec20]

Kibana version: 7.5.0-SNAPSHOT "build_hash" : "ecb20ebc6cb155be37ecdc68ca8a178531744758", "build_date" : "2019-10-10T09:21:05.340310Z"

Original install method (e.g. download page, yum, from source, etc.): tar.gz

Describe the usability bug:

In the UI, a failed transform must first be stopped before it can be deleted. This is a two step process.

However, the API now allows DELETE ?force=true and therefore we should allow the user of the UI to delete a failed transform without having to stop it first.

(Note: The user may also want to reset a transform from its FAILED state back to STOPPED therefore the option to stop it is still valid. This is still a bit of an odd user experience as stopping something that has failed isn't intuitive, however as this change involves the API too, it should be the subject of a different ticket).

[elasticmachine]

Pinging @elastic/ml-ui (:ml)

[peteharverson]

Closing as fixed for 7.9.0 by #69472