[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.

test/SourceKit/SyntaxMapData/syntaxmap-object-literals.swift

@@ -1,4 +1,4 @@
-// RUN: %sourcekitd-test -req=syntax-map %s > %t.response
+// RUN: %sourcekitd-test -req=syntax-map %s | %sed_clean > %t.response
 // RUN: diff -u %s.response %t.response
 
-let x = [#Cloud(tube: true)#]
+let x = #Cloud(tube: true)