Nested-objects-encoding

[joshuat]

Carries over changes from parse-community#8209 to fix encoding of nested objects, specifically dates.

[richardharrington]

lol this seems like a pretty major oversight for them not to have taken care of in the first place.

Ideally we'd merge this into the 4.3.0-hustle-9.1 branch as well, but these branches are kind of a shit show and we've sort of abandoned the idea of adding to that branch -- which is not working for obscure reasons -- until we get off parse server (or until we have three months till the Mongo upgrade and we haven't made any progress on Parsectomy and we start panicking again).

I was planning to do a short timebox for some possible quick fixes to 4.3.0-hustle-9.1 anyway, so I'll make sure to cherry-pick this over if I do. Or rebase it on 4.3.0-hustle-8, or whatever.