[BSP] Make MessageRegistry.bspProtocol a static stored property

This should be an immutable value and `MessageRegistry.init()` is not a
trivial constructor. No reason to keep it a computed property.

Also, Move `MessageRegistry.lspProtocol` to
LanguageServerProtocol/Messages.swift to align with the BSP couterpart.

Author: rintaro

Sources/BuildServerProtocol/Messages.swift

@@ -41,10 +41,9 @@ private let notificationTypes: [NotificationType.Type] = [
 ]
 
 extension MessageRegistry {
-  public static var bspProtocol: MessageRegistry {
+  public static let bspProtocol: MessageRegistry =
     MessageRegistry(requests: requestTypes, notifications: notificationTypes)
-  }
 }
 
 @available(*, deprecated, message: "use MessageRegistry.bspProtocol instead")
-public let bspRegistry = MessageRegistry(requests: requestTypes, notifications: notificationTypes)
+public let bspRegistry = MessageRegistry.bspProtocol

Sources/LanguageServerProtocol/MessageRegistry.swift

@@ -11,10 +11,6 @@
 //===----------------------------------------------------------------------===//
 
 public final class MessageRegistry: Sendable {
-
-  public static let lspProtocol: MessageRegistry =
-    MessageRegistry(requests: builtinRequests, notifications: builtinNotifications)
-
   private let methodToRequest: [String: _RequestType.Type]
   private let methodToNotification: [String: NotificationType.Type]
 

Sources/LanguageServerProtocol/Messages.swift

@@ -128,6 +128,11 @@ public let builtinNotifications: [NotificationType.Type] = [
   WorkDoneProgress.self,
 ]
 
+extension MessageRegistry {
+  public static let lspProtocol: MessageRegistry =
+    MessageRegistry(requests: builtinRequests, notifications: builtinNotifications)
+}
+
 // MARK: Miscellaneous Message Types
 
 public struct VoidResponse: ResponseType, Hashable {