flow: Upgrade to v0.170

[chrisbobbe]

This is the Flow version used by React Native 68.

It's a surprisingly easy upgrade this time, following the recent Expo 45 upgrade (#5507), which caused fbemitter to be bumped such that it no longer used Flow's legacy "weak" mode, removed in Flow v0.166.

[gnprice]

Neat, thanks!

I'm scanning through the Flow release notes, from 0.162.1 on up to 0.170.0. Things I spot:

• The deprecated * type is now an alias to any. You can use flow codemod replace-existentials, which is available in previous versions of Flow, to upgrade your codebase to not use *. This codemod command will not be available in the current or future versions of Flow.

  I tried this codemod out, and it didn't touch anything. To make sure I was using it right, I edited a type annotation somewhere to say * instead of a real type, and then ran the codemod:
  $ time npx flow codemod replace-existentials --write src/
  and it successfully edited the * back to the appropriate real type:

  --- a/src/compose/ComposeBox.js
  +++ b/src/compose/ComposeBox.js
  @@ -138,1 +138,1 @@ function getQuoteAndReplyText(args: {|
  -  realm: *,
  +  realm: URL,

• Add $ObjMapConst<O, T> builtin type, alias for $ObjMap<O, () => T>.

  Seems handy. git grep -w ObjMap finds one spot that could use it.

OK, and that's it.

Scanning forward, it looks like 0.175.1 is the one that should make things more pleasant when working with TsFlower, reducing the need to do flow stop; flow start:

Fix an incremental bug which would sometimes cause Flow to choose the wrong provider for a haste module, most commonly when one of those providers is a .js.flow file.

[gnprice]

And merged.

[chrisbobbe]

Great, thanks for the review!