Zenoh router adminspace queries timeout when run on a one core host with storages

[OlivierHecart]

Describe the bug

When run on a one core host with a storage plugin, queries on admin space timeout.

This seems to be due to async-std not starting runtime worker threads in those conditions.

Until eventually ported to tokio, plugins using async-std might workaround the issue by calling a macro similar to the following one at startup: https://github.com/eclipse-zenoh/zenoh/blob/d6da961ad59954ffc19245bbdb6547f8a6bd7d73/commons/zenoh-core/src/macros.rs#L176

To reproduce

1. start a Zenoh router one a one core host with storage plugin and configured storages.
2. query the adminspace (@/**)

System info

• Platform: docker container with 1 CPU
• Zenoh version: 0.11.0