Format object patterns.

[kallentu]

• Added ObjectPatterns to canBlockSplit.
• Migrated object pattern tests and object patterns with comments tests.

There's one test case in there that's not great, but I think it's a general problem with ListPattern, MapPattern too.
Maybe revisit it with the other patterns in another CL.

>>> Split in type argument.
if (obj case LongClassName<First, Second>()) {;}
<<<
### TODO(tall): It formats like this if there's no elements. Similarly with lists, maps etc.
if (obj
    case LongClassName<
        First,
        Second
        >()) {
  ;
}

[munificent]

TODO(tall): It formats like this if there's no elements. Similarly with lists, maps etc.

if (obj
case LongClassName<
First,
Second
>()) {
;
}

Yeah, that looks like an ugly corner case of the collapsible indentation stuff I did. Leaving a TODO sounds good. I'll try to take a look at some point.