[Parser] Stop creating PoundFile(ID|Path|)Syntax nodes.

All of these are subsumed by macro expansion expressions.

Author: DougGregor

Sources/SwiftParser/Expressions.swift

@@ -1017,24 +1017,6 @@ extension Parser {
         poundFile: tok,
         arena: self.arena
       ))
-    case (.poundFileIDKeyword, let handle)?:
-      let tok = self.eat(handle)
-      return RawExprSyntax(RawPoundFileIDExprSyntax(
-        poundFileID: tok,
-        arena: self.arena
-      ))
-    case (.poundFileKeyword, let handle)?:
-      let tok = self.eat(handle)
-      return RawExprSyntax(RawPoundFileExprSyntax(
-        poundFile: tok,
-        arena: self.arena
-      ))
-    case (.poundFilePathKeyword, let handle)?:
-      let tok = self.eat(handle)
-      return RawExprSyntax(RawPoundFilePathExprSyntax(
-        poundFilePath: tok,
-        arena: self.arena
-      ))
     case (.__function__Keyword, let handle)?:
       let tok = self.eat(handle)
       return RawExprSyntax(RawPoundFunctionExprSyntax(

Sources/SwiftParser/Lexer.swift

@@ -1540,9 +1540,6 @@ extension Lexer.Cursor {
     switch literal {
     case "keyPath": kind = .poundKeyPathKeyword
     case "selector": kind = .poundSelectorKeyword
-    case "file": kind = .poundFileKeyword
-    case "fileID": kind = .poundFileIDKeyword
-    case "filePath": kind = .poundFilePathKeyword
     case "assert": kind = .poundAssertKeyword
     case "sourceLocation": kind = .poundSourceLocationKeyword
     case "warning": kind = .poundWarningKeyword

Sources/SwiftParser/RawTokenKindSubset.swift

@@ -738,9 +738,6 @@ enum PrimaryExpressionStart: RawTokenKindSubset {
   case nilKeyword
   case period
   case pound
-  case poundFileIDKeyword
-  case poundFileKeyword
-  case poundFilePathKeyword
   case poundKeyPathKeyword
   case poundSelectorKeyword
   case prefixPeriod
@@ -771,9 +768,6 @@ enum PrimaryExpressionStart: RawTokenKindSubset {
     case .nilKeyword: self = .nilKeyword
     case .period: self = .period
     case .pound: self = .pound
-    case .poundFileIDKeyword: self = .poundFileIDKeyword
-    case .poundFileKeyword: self = .poundFileKeyword
-    case .poundFilePathKeyword: self = .poundFilePathKeyword
     case .poundKeyPathKeyword: self = .poundKeyPathKeyword
     case .poundSelectorKeyword: self = .poundSelectorKeyword
     case .prefixPeriod: self = .prefixPeriod
@@ -807,9 +801,6 @@ enum PrimaryExpressionStart: RawTokenKindSubset {
     case .nilKeyword: return .nilKeyword
     case .period: return .period
     case .pound: return .pound
-    case .poundFileIDKeyword: return .poundFileIDKeyword
-    case .poundFileKeyword: return .poundFileKeyword
-    case .poundFilePathKeyword: return .poundFilePathKeyword
     case .poundKeyPathKeyword: return .poundKeyPathKeyword
     case .poundSelectorKeyword: return .poundSelectorKeyword
     case .prefixPeriod: return .prefixPeriod