Now Thread Pool for Remoting is publicly accessible, and there are lots of misuses in plugins. The approach should be improved.

Proposed changes:

• Restrict the public field
• Add method, which allows to get Remoting thread pool
• Explicitly document allowed usages in Javadoc for the new method

To consider:

• Isolate Remoting Thread pool and prohibit it's usage by plugins by default. It may be problematic since there are lots of valid usages in detached plugins and core modules
• Introduce a new thread pool for Remoting-unrelated cases