An option to run one-shot instances

### What feature do you want to see added?

Currently there are two shutdown policies -- timeout-based and billing-based. However, even with a minimal timeout and number of executors=1, there is a very real possibility that the next queued build will pick up an instance which just went idle. This is not always acceptable, some builds require a new machine for every run.

In GCP plugin it is a boolean option "one shot", in AWS a numeric "Maximum total uses". It could be something like that, or another option in the shutdown policy, e.g. "immediately after the build" (as long as it ensures that the instance definitely becomes unusable right after the build, to avoid a race condition).

### Upstream changes

_No response_

### Are you interested in contributing this feature?

_No response_