Prototype / Early Access use of virtual threads (loom, fibers)

[barchetta]

Prototype support for using virtual threads in Helidon. Ideally we would release early access modules that when used with an early access Loom release allows experimentation with virtual threads.

Some ideas:

• Helidon MP: Supply an UnboundedExecutor for the JAX-RS executor Loom support moved to ThreadPoolSupplier #3164
• Common: Supply an UnboundedExecutor via common.configurable.ThreadPoolSupplier Loom support moved to ThreadPoolSupplier #3164
• Helidon SE: Support passing ExecutorService when registering Service Ability to declare ExecutorService while registering Service in HelidonSE #1327
• Distribution: explore ways to make above early access features available to Helidon customers.
• Netty: investigate/experiment Netty support for virtual threads
• Other Fibers and Helidon #549