MessageType should include a 'trace' severity

MessageType (as of 3.18) is defined as:

export namespace MessageType {
	/**
	 * An error message.
	 */
	export const Error = 1;
	/**
	 * A warning message.
	 */
	export const Warning = 2;
	/**
	 * An information message.
	 */
	export const Info = 3;
	/**
	 * A log message.
	 */
	export const Log = 4;
	/**
	 * A debug message.
	 *
	 * @since 3.18.0
	 */
	export const Debug = 5;
}

export type MessageType = 1 | 2 | 3 | 4 | 5;

The "debug" addition is handy, but it'd be great if one more level, 'trace' was also added. VS Code's newish support for logging output window has a distinction of debug versus trace:

And .NET's logging library similarly has a debug vs. trace distinction in this enum:
https://learn.microsoft.com/en-us/dotnet/api/microsoft.extensions.logging.loglevel?view=net-9.0-pp

As it stands, for us to report 'trace' events with the standard logging API, we're mapping those back to 'debug' which is slightly confusing when we're comparing logs from other sources. Given both sides have a 'trace' concept it'd be nice if we could just use it.

As we discovered, the generic 'log' message type doesn't really mean trace, but rather it has no severity, and it gets logged by the VS Code LSP client without any severity tag at all.

Locate the MessageType definition in the TypeScript protocol sources and review how its constants and union type are tested or published. Check the existing Debug addition and the referenced VS Code client behavior before assessing compatibility. Done means the protocol exposes a distinct trace severity without changing the meaning of Log.