BasicFormat does not add whitespace between end of previous closure and argument name for multi-trailing closures

[bnbarham]

func testMultiTrailingClosure() {
  var input = Parser("""
    foo { _ in
    }anotherClosure: { _ in
    }
    """)
  let call = ExprSyntax.parse(from: &input)

  let formatted = call.formatted()
  assertStringsEqualWithDiff(formatted.description, """
    foo { _ in
    } anotherClosure: { _ in
    }
    """)
}

Produces:

failed - Actual output (+) differed from expected output (-):
–foo { _ in
–} anotherClosure: { _ in
+foo { _ in 
+}anotherClosure: { _ in 
 }

ie. extra space after in and no space after }.

[ahoppen]

rdar://107454729

[ahoppen]

Fixed by #1569.