As part of java completions for expected types, if the expected type is
a functional interface, lambda expression completions are suggested with
parameters.

Change-Id: I59a0e94171d1c98b18a21c9009498c64ee6cad02
Signed-off-by: Gayan Perera <gayanper@gmail.com>
Reviewed-on: https://git.eclipse.org/r/c/jdt/eclipse.jdt.core/+/186546
Tested-by: JDT Bot <jdt-bot@eclipse.org>