[stdlib] Better diagnosis for unavailable APIs

Added tests for expected-error and fix-its.

- Add arguments signature regardless that is the same as before.
  Because the error message looks more natural.
  e.g. "makeIterator" => "makeIterator()",
  "replaceSubrange" => "replaceSubrange(_:with:)"
- Any${ExistentialCollection}.underestimateCount() was a method, not
  computed property.
- 'LazySequenceType' has been renamed to 'LazySequenceProtocol', but not
  'LazyCollectionProtocol'
- Streamable.writeTo(_:) had no argument label.
- Fixed typo in print() debugPrint() error message (not working for now)
- Repeated.init(): changed `renamed` to `message` because the arugment
  order has changed.
- Marked `public` for some unavailable method on `Sequence`
- Sequence.split(_:maxSplit:allowEmptySlices) was replaced with
  split(separator:maxSplits:omittingEmptySubsequences:),
  not split(separator:omittingEmptySubsequences:isSeparator:)
- Sequence.split(_:allowEmptySlices:isSeparator) was replaced with
  split(maxSplits:omittingEmptySubsequences:isSeparator:),
  not split(_:omittingEmptySubsequences:isSeparator:)
- Sequence.startsWith(_:isEquivalent:) or startsWith(_:) had no label on
  the first argument.
- transcode(_:_:_:_:stopOnError), not transcode(_:_:_:_:stoppingOnError)
- Removed mutating methods from UnsafePointer.
  alloc(_:), dealloc(_:), setter:memory, initialize(_:), destroy(),
  and destroy(_:)

stdlib/public/core/Unicode.swift

@@ -1186,7 +1186,7 @@ public typealias UnicodeCodecType = UnicodeCodec
 public func transcode<Input, InputEncoding, OutputEncoding>(
   _ inputEncoding: InputEncoding.Type, _ outputEncoding: OutputEncoding.Type,
   _ input: Input, _ output: (OutputEncoding.CodeUnit) -> Void,
-  stoppingOnError stopOnError: Bool
+  stopOnError: Bool
 ) -> Bool
   where
   Input : IteratorProtocol,