fix(types): add Boolean signature to filter

[cartant]

Closes #4959

Description:

This PR adds another signature overload to filter to match Boolean predicates. This solves the problem identified in #4959 and is sufficiently specific that I cannot foresee it effecting further problems.

I've added a conventional test and a dtslint test.

Other operators that have a similar issue are: find, first, last and takeWhile. If this fix is approved, I'll have a look at what can be done for those (first and last are a little more complicated, as they support a default value).

@benlesh @rkirov

Related issue (if exists): #4959

[rkirov]

Looks good to me, I will downstream this to google internal to unblock the TS3.5 migration.

[benlesh]

Should we also do this for other operators with predicates? Like first, last, etc?

[cartant]

Should we also do this for other operators with predicates? Like first, last, etc?

Yeah. We should use this approach for find, first, last and takeWhile - those are the only other operators that accept a user-defined type guard. I was waiting to hear back from Rado, as some of those other operators are a little more complicated - as they support default values - and didn't want to prep type changes if they weren't gonna do the job. But if the Google code base is now synced, I guess we should look at change 'em, too.