Respect Lua.trace.server=verbose to enable verbose LSP logging

I'm trying to read the LSP traffic when using VSCode.
Other languages support a `.trace.server` setting, see https://code.visualstudio.com/api/language-extensions/language-server-extension-guide#logging-support-for-language-server
Setting it to `"verbose"` should log all JSON-RPC LSP message.

The Lua server log has some info but not all and I'd like to avoid using something that's specific to the language server here.

Start by locating the VSCode extension's handling of the Lua.trace.server setting and compare it with the linked language-server logging guidance. Done means selecting "verbose" causes all JSON-RPC LSP messages to be logged, rather than relying on language-server-specific logging.

Written by the indexing model from the issue text.