Refactor Error Code definitions

[Seelengrab]

This refactors the way error codes are handled, in preparation for making JSONRPC.jl less LSP specific, by hooking into custom error printing provided by an upstream PR. Requires julia-vscode/JSONRPC.jl#70.

[Seelengrab]

There's also these error codes that seem to overlap considerably:

LanguageServer.jl/src/requests/features.jl

Lines 155 to 167 in e67befb

	function textDocument_formatting_request(params::DocumentFormattingParams, server::LanguageServerInstance, conn)
	doc = getdocument(server, params.textDocument.uri)
	newcontent = try
	config = get_juliaformatter_config(doc, server)
	format_text(get_text(doc), params, config)
	catch err
	return JSONRPC.JSONRPCError(
	-32000,
	"Failed to format document: $err.",
	nothing
	)
	end

This error code is seemingly used for a formatting failure, but the LSP spec says this specific code should not be used:

/**
 * This is the end range of JSON-RPC reserved error codes.
 * It doesn't denote a real error code.
 *
 * @since 3.16.0
 */
export const jsonrpcReservedErrorRangeEnd = -32000;

This should probably be changed to some other error code, but I don't know how that would interact with the extension.

Similarly, this section also defines a new error code for formatting:

LanguageServer.jl/src/requests/features.jl

Lines 207 to 217 in e67befb

	# Format the full marked text
	text_formatted = try
	config = get_juliaformatter_config(doc, server)
	format_text(text_marked, params, config)
	catch err
	return JSONRPC.JSONRPCError(
	-33000,
	"Failed to format document: $err.",
	nothing
	)
	end

This doesn't conflict with the spec, but it doesn't match the existing formatting error code used above. This needs a decision on whether they should be merged into one error code, or kept distinct.

[pfitzseb]

Both of those should be -33000 I think. As far as I'm aware no-one is actually checking for the specific error code anyways, FWIW.