Add logLevel and logFile extension setting

[dhruvmanila]

Summary

This PR adds ruff.logLevel and ruff.logFile settings to the VS Code extension which corresponds to the same for the ruff server. Without these, there's no way to configure the log level and the destination for the log messages unlike other editors.

Test Plan

Using the following config:

{
  "ruff.logLevel": "debug",
  "ruff.logFile": "~/playground/ruff/server.logs",
  "ruff.trace.server": "messages"
}

I confirmed that it outputs the logs messages at the specified location.

[MichaReiser]

What's the relationship of the new logLevel setting to the tracing setting?

[dhruvmanila]

What's the relationship of the new logLevel setting to the tracing setting?

The ruff.server.trace value is either off | messages | verbose where

• off doesn't emit any log messages
• messages will only emit the type of request and response along with Ruff server's log messages but only at INFO or above
• verbose will emit the request and response parameters as well

Ruff server also emits trace messages at different levels, specifically DEBUG level but there's no way to update that from VS Code. This is different in other editors where a user can update the logLevel server setting.

Only updating the logLevel doesn't make any difference, it should be combined with updating the ruff.server.trace to messages or verbose for Ruff to emit the messages at the specified logLevel.

[dhruvmanila]

Actually, this is incorrect. It seems that the logLevel and logFile settings in the server code is only taken from the global settings i.e., they aren't resolve per workspace which makes sense. So, we can't allow VS Code variables in here. I'll revert this.