Hook up user specified options of air.logLevel and air.dependencyLogLevels in VS Code extension

[DavisVaughan]

See #93 for more

The server side is mostly ready to go, but we need to create client and server representations of "client settings" like

ClientSettings {
  logLevel: Option<LogLevel>,
  dependencyLogLevels: Option<String>
}

Note that every field in ClientSettings should be optional. This allows:

• Easier backwards compat
• Partial initialization like in Zed's initialization_options setting

We will pass the settings through InitializeParams.initializationOptions, which is an "any" type field we are allowed to control