delete all instances at once

It'd be nice to delete all instances at once by using --all flag provided in the delete command.

```shell
$ limactl list
NAME STATUS SSH ARCH CPUS MEMORY DISK DIR
buildkit Stopped 127.0.0.1:0 x86_64 4 4GiB 100GiB /Users/batuhan.apaydin/.lima/buildkit
default Stopped 127.0.0.1:0 x86_64 4 4GiB 100GiB /Users/batuhan.apaydin/.lima/default

$ limactl delete --all
INFO[0000] The QEMU process seems already stopped
INFO[0000] The host agent process seems already stopped
INFO[0000] Removing *.pid *.sock under "/Users/batuhan.apaydin/.lima/buildkit"
INFO[0000] Removing "/Users/batuhan.apaydin/.lima/buildkit/ha.sock"
INFO[0000] Deleted "buildkit" ("/Users/batuhan.apaydin/.lima/buildkit")

INFO[0000] The QEMU process seems already stopped
INFO[0000] The host agent process seems already stopped
INFO[0000] Removing *.pid *.sock under "/Users/batuhan.apaydin/.lima/default"
INFO[0000] Deleted "default" ("/Users/batuhan.apaydin/.lima/default")
```

- [ ] limactl delete --all should show a warning and an "Are you sure?" prompt and require a --tty=false option to skip the prompt.
- [ ] limactl delete --all --force, should remove all the instances even if they are working, once we remove the --force flag, it should prompt an info message to warn me there are some working instances, are you ok to delete them?
- [ ] limactl delete --all something to be an error; if you specify --all, you must not specify any instance names.