[Feature] ServerInfo request

For monitoring and troubleshooting the Language Server, it is extremely useful to have server information printer in the editor. Most Vim clients either don't provide any way of printing out LSP server address, log file, etc or use their own format (e.g. here's my request for a Vim client). It might be useful for both users and LSP developers to provide a unified request (workspace/serverInfo?) and server information format. There are few things we could ask from every server:

• Server PID (so that I could attach my debugger to the process)
• Log files: both stdout and sterr files
• URL
• Memory consumption
• Additional (optional) server information string which can be specific to each server (e.g. which one is used, what the version is, etc)

Having this information would provide better user experience for bug submissions and better developer experience. Alternatively, we could allow servers to return a string in free format letting each server decide what they would like to expose to the client.

This is an example of server information printer in Vim's YouCompleteMe:

Start by reviewing the proposed workspace/serverInfo request and the listed server details: PID, logs, URL, memory, and an optional information string. Done means agreeing on a unified request and response format, including whether free-form server output is supported, and updating the protocol specification accordingly.