Add RequestFailed and ServerCancelled LSP specific error codes?

[DavisVaughan]

I see these two LSP specific error codes:

tower-lsp/src/jsonrpc/error.rs

Lines 31 to 42 in 49e1ce5

	/// The request was cancelled by the client.
	///
	/// # Compatibility
	///
	/// This error code is defined by the Language Server Protocol.
	RequestCancelled,
	/// The request was invalidated by another incoming request.
	///
	/// # Compatibility
	///
	/// This error code is specific to the Language Server Protocol.
	ContentModified,

In 3.17 we got a few more:
https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#responseMessage

Notably:

/**
	 * A request failed but it was syntactically correct, e.g the
	 * method name was known and the parameters were valid. The error
	 * message should contain human readable information about why
	 * the request failed.
	 *
	 * @since 3.17.0
	 */
	export const RequestFailed: [integer](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#integer) = -32803;

	/**
	 * The server cancelled the request. This error code should
	 * only be used for requests that explicitly support being
	 * server cancellable.
	 *
	 * @since 3.17.0
	 */
	export const ServerCancelled: [integer](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#integer) = -32802;

Would it make sense to add these in?