Fix RawSyntax's leading/trailingTrivia computation to return nil if its outermost children don't have leading/trailing trivia

Previously if would skip over outer children that didn't have leading/trailing
trivia until it found one that did. This was causing that trivia to be included
twice when computing the totalLength/byteSize of the node; once in
leading/trailingTrivia and again in contentlength, which only skipped the trivia
of the outmost children.

Author: Nathan Hawes

Sources/SwiftSyntax/RawSyntax.swift

@@ -350,7 +350,7 @@ extension RawSyntax {
     case .node(_, let layout):
       for child in layout {
         guard let child = child else { continue }
-        guard let result = child.leadingTrivia else { continue }
+        guard let result = child.leadingTrivia else { break }
         return result
       }
       return nil
@@ -364,7 +364,7 @@ extension RawSyntax {
     case .node(_, let layout):
       for child in layout.reversed() {
         guard let child = child else { continue }
-        guard let result = child.trailingTrivia else { continue }
+        guard let result = child.trailingTrivia else { break }
         return result
       }
       return nil

Tests/SwiftSyntaxTest/Inputs/visitor.swift

@@ -1,5 +1,5 @@
 func foo() {
-  func foo() {
+  public func foo() {
     func foo() {
       /*Unknown token */0xG
     }