lib: add function `log` to `LONG_RUNNING` API
lib: add `State.long_running_log`
lib: improve display of targets
test: override configuration everywhere in `cli.ml`
lib: add the “follow-dependencies” navigation
lib: refactor code of the `Explorer`
lib: add function `Time.log`
lib: add display of target status
lib: add the `explore` sub-command
lib: fix display bugs in the Target-Explorer
lib: improve UX of target-filter picking
lib: add function `Host.to_uri` (and use in `log`)
lib: add function `Target.latest_run_parameters`
lib: add “additional queries” to long-runnings

These queries can be called from the Target Explorer.