112.06.00

- Support for user control of stale-artifact deletion, by allowing
  specification of an artifact-determination policy.
- Expose jenga's internal (and better - only quotes when necessary)
  definition of `Shell.escape` in `Api`
- Removed `Action.shell` from the API, superseded by `Action.process`.
- Changed RPC interface as needed for build manager to switch from
  scraping error messages to RPCs.
- Fixed jenga's per-rule memo table, which mistakenly kept stale values.
- Show what target is being demanded, useful for debugging rules.
- Run user action when persistent format changes.
- When filtering buildable targets by globs, pay attention to the kinds
  allowed by the glob.

    Specifically, if the kinds don't include `` `File `` (i.e. only
    include `` `Directory ``) then we should not see any
    `buildable_targets` in the filtered list.