Language server protocol is being violated over stdio

[parkuman]

When in stdio mode using the --stdio flag, any LSP client expects all messages from the server to start with Content-Length.

The following two lines violate this protocol by printing non-LSP-compliant stuff to stdio:

• https://github.com/CircleCI-Public/circleci-yaml-language-server/blob/main/pkg/server/server.go#L29
• https://github.com/CircleCI-Public/circleci-yaml-language-server/blob/main/pkg/server/server.go#L92

This results in the following error for clients on stdio:

Content-Length not found in header: New client connection
Called method: initialize
Content-Length: 694

We need a nice way to handle (or outright ignore) debugging output when in stdio mode. We should also implement some sort of safeguard such that someone can't accidentally add a new stdout a few years down the line and breaks stdio mode for all the stdio-using clients