[WIP] Implement SE-0039 (Modernizing Playground Literals) (#2215)

* Implement the majority of parsing support for SE-0039.

* Parse old object literals names using new syntax and provide FixIt.

For example, parse "#Image(imageLiteral:...)" and provide a FixIt to
change it to "#imageLiteral(resourceName:...)".  Now we see something like:

test.swift:4:9: error: '#Image' has been renamed to '#imageLiteral
var y = #Image(imageLiteral: "image.jpg")
        ^~~~~~ ~~~~~~~~~~~~
        #imageLiteral resourceName

Handling the old syntax, and providing a FixIt for that, will be handled in a separate
commit.

Needs tests.  Will be provided in later commit once full parsing support is done.

* Add back pieces of syntax map for object literals.

* Add parsing support for old object literal syntax.

... and provide fixits to new syntax.

Full tests to come in later commit.

* Improve parsing of invalid object literals with old syntax.

* Do not include bracket in code completion results.

* Remove defunct code in SyntaxModel.

* Add tests for migration fixits.

* Add literals to code completion overload tests.

@akyrtzi told me this should be fine.

* Clean up response tests not to include full paths.

* Further adjust offsets.

* Mark initializer for _ColorLiteralConvertible in UIKit as @nonobjc.

* Put attribute in the correct place.

stdlib/public/core/CompilerProtocols.swift

@@ -197,21 +197,21 @@ public protocol StringInterpolationConvertible {
 }
 
 /// Conforming types can be initialized with color literals (e.g.
-/// `[#Color(colorLiteralRed: 1, green: 0, blue: 0, alpha: 1)#]`).
+/// `#colorLiteral(red: 1, green: 0, blue: 0, alpha: 1)`).
 public protocol _ColorLiteralConvertible {
-  init(colorLiteralRed: Float, green: Float, blue: Float, alpha: Float)
+  init(red: Float, green: Float, blue: Float, alpha: Float)
 }
 
 /// Conforming types can be initialized with image literals (e.g.
-/// `[#Image(imageLiteral: "hi.png")#]`).
+/// `#imageLiteral(resourceName: "hi.png")`).
 public protocol _ImageLiteralConvertible {
-  init(imageLiteral: String)
+  init(resourceName: String)
 }
 
 /// Conforming types can be initialized with strings (e.g.
-/// `[#FileReference(fileReferenceLiteral: "resource.txt")#]`).
+/// `#fileLiteral(resourceName: "resource.txt")`).
 public protocol _FileReferenceLiteralConvertible {
-  init(fileReferenceLiteral: String)
+  init(resourceName: String)
 }
 
 /// A container is destructor safe if whether it may store to memory on