Add extension identifier to builtin extensions

Author: intitni

Tool/Sources/BuiltinExtension/BuiltinExtension.swift

@@ -6,6 +6,8 @@ import Preferences
 public protocol BuiltinExtension: CopilotForXcodeExtensionCapability {
     /// An id that let the extension manager determine whether the extension is in use.
     var suggestionServiceId: BuiltInSuggestionFeatureProvider { get }
+    /// An identifier for the extension.
+    var extensionIdentifier: String { get }
 
     /// All chat builders provided by this extension.
     var chatTabTypes: [any ChatTab.Type] { get }

Tool/Sources/CodeiumService/CodeiumExtension.swift

@@ -12,6 +12,8 @@ import Workspace
 }
 
 public final class CodeiumExtension: BuiltinExtension {
+    public var extensionIdentifier: String { "com.codeium" }
+    
     public var suggestionServiceId: Preferences.BuiltInSuggestionFeatureProvider { .codeium }
 
     public let suggestionService: CodeiumSuggestionService?

Tool/Sources/GitHubCopilotService/GitHubCopilotExtension.swift

@@ -7,6 +7,8 @@ import Preferences
 import Workspace
 
 public final class GitHubCopilotExtension: BuiltinExtension {
+    public var extensionIdentifier: String { "com.github.copilot" }
+    
     public var suggestionServiceId: Preferences.BuiltInSuggestionFeatureProvider { .gitHubCopilot }
 
     public let suggestionService: GitHubCopilotSuggestionService?