[CodeGeneration] Stop generating add{ElementName}(_:) methods

CodeGeneration/Sources/SyntaxSupport/AttributeNodes.swift

@@ -187,11 +187,7 @@ public let ATTRIBUTE_NODES: [Node] = [
       ),
       Child(
         name: "availabilityArguments",
-        kind: .collection(
-          kind: .availabilityArgumentList,
-          collectionElementName: "AvailabilityArgument",
-          deprecatedCollectionElementName: "Availability"
-        )
+        kind: .collection(kind: .availabilityArgumentList)
       ),
       Child(
         name: "semicolon",
@@ -257,11 +253,7 @@ public let ATTRIBUTE_NODES: [Node] = [
       ),
       Child(
         name: "platforms",
-        kind: .collection(
-          kind: .platformVersionItemList,
-          collectionElementName: "Platform",
-          deprecatedCollectionElementName: "Availability"
-        ),
+        kind: .collection(kind: .platformVersionItemList),
         documentation: "The list of OS versions in which the declaration became ABI stable."
       ),
     ],
@@ -500,7 +492,7 @@ public let ATTRIBUTE_NODES: [Node] = [
       ),
       Child(
         name: "arguments",
-        kind: .collection(kind: .differentiabilityArgumentList, collectionElementName: "Argument"),
+        kind: .collection(kind: .differentiabilityArgumentList),
         documentation: "The parameters for differentiation."
       ),
       Child(
@@ -827,7 +819,7 @@ public let ATTRIBUTE_NODES: [Node] = [
       ),
       Child(
         name: "platforms",
-        kind: .collection(kind: .platformVersionItemList, collectionElementName: "Platform")
+        kind: .collection(kind: .platformVersionItemList)
       ),
     ]
   ),

CodeGeneration/Sources/SyntaxSupport/AvailabilityNodes.swift

@@ -175,7 +175,7 @@ public let AVAILABILITY_NODES: [Node] = [
       ),
       Child(
         name: "components",
-        kind: .collection(kind: .versionComponentList, collectionElementName: "VersionComponent"),
+        kind: .collection(kind: .versionComponentList),
         documentation:
           "Any version components that are not the major version . For example, for `1.2.0`, this will contain `.2.0`."
       ),

CodeGeneration/Sources/SyntaxSupport/Child.swift

@@ -43,12 +43,7 @@ public enum ChildKind {
   case nodeChoices(choices: [Child], childHistory: Child.History = [])
   // FIXME: We don't appear to have ever generated compatibility layers for children of node choices!
   /// The child is a collection of `kind`.
-  case collection(
-    kind: SyntaxNodeKind,
-    collectionElementName: String? = nil,
-    defaultsToEmpty: Bool = false,
-    deprecatedCollectionElementName: String? = nil
-  )
+  case collection(kind: SyntaxNodeKind, defaultsToEmpty: Bool = false)
   /// The child is a token that matches one of the given `choices`.
   /// If `requiresLeadingSpace` or `requiresTrailingSpace` is not `nil`, it
   /// overrides the default leading/trailing space behavior of the token.
@@ -132,7 +127,7 @@ public class Child: NodeChoiceConvertible {
       return kind
     case .nodeChoices:
       return .syntax
-    case .collection(kind: let kind, _, _, _):
+    case .collection(kind: let kind, _):
       return kind
     case .token:
       return .token
@@ -268,7 +263,7 @@ public class Child: NodeChoiceConvertible {
   /// Whether this child has syntax kind `UnexpectedNodes`.
   public var isUnexpectedNodes: Bool {
     switch kind {
-    case .collection(kind: .unexpectedNodes, _, _, _):
+    case .collection(kind: .unexpectedNodes, _):
       return true
     default:
       return false
@@ -283,7 +278,7 @@ public class Child: NodeChoiceConvertible {
       return choices.isEmpty
     case .node(let kind):
       return kind.isBase
-    case .collection(kind: let kind, _, _, _):
+    case .collection(kind: let kind, _):
       return kind.isBase
     case .token:
       return false
@@ -354,7 +349,7 @@ public class Child: NodeChoiceConvertible {
 
     self.init(
       name: name,
-      kind: .collection(kind: .unexpectedNodes, collectionElementName: name.withFirstCharacterUppercased),
+      kind: .collection(kind: .unexpectedNodes),
       experimentalFeature: earlier?.experimentalFeature ?? later?.experimentalFeature,
       nameForDiagnostics: nil,
       documentation: nil,

CodeGeneration/Sources/SyntaxSupport/CommonNodes.swift

@@ -69,7 +69,7 @@ public let COMMON_NODES: [Node] = [
       ),
       Child(
         name: "statements",
-        kind: .collection(kind: .codeBlockItemList, collectionElementName: "Statement"),
+        kind: .collection(kind: .codeBlockItemList),
         nameForDiagnostics: "statements"
       ),
       Child(
@@ -201,13 +201,13 @@ public let COMMON_NODES: [Node] = [
     children: [
       Child(
         name: "attributes",
-        kind: .collection(kind: .attributeList, collectionElementName: "Attribute", defaultsToEmpty: true),
+        kind: .collection(kind: .attributeList, defaultsToEmpty: true),
         documentation:
           "If there were standalone attributes without a declaration to attach them to, the ``MissingDeclSyntax`` will contain these."
       ),
       Child(
         name: "modifiers",
-        kind: .collection(kind: .declModifierList, collectionElementName: "Modifier", defaultsToEmpty: true),
+        kind: .collection(kind: .declModifierList, defaultsToEmpty: true),
         documentation:
           "If there were standalone modifiers without a declaration to attach them to, the ``MissingDeclSyntax`` will contain these."
       ),

CodeGeneration/Sources/SyntaxSupport/CompilerNodes.swift

@@ -87,10 +87,7 @@ public let COMPILER_NODES: [Node] = [
     children: [
       Child(
         name: "attributes",
-        kind: .collection(
-          kind: .attributeList,
-          collectionElementName: "Attribute"
-        )
+        kind: .collection(kind: .attributeList)
       ),
       Child(
         name: "modifiers",