Migrate more MapLikes to Maps

[rbuckton]

This change migrates a number of remaining MapLike<T> entries to Map<T>, as well as adds a number of additional functions for working with both MapLike<T> and Map<T>.

The changes in the compiler itself add an additional performance improvement, shaving another ~400ms off of the total emit time of Monaco and Angular.

This also disables the tslint restriction on use of the in operator, as offline performance tests I've run show that using in is faster than both hasOwnProperty and obj[key] when merely testing for the presence of a key. The in operator also works better when paired with delete, which is faster at removing entries from a Map<T> than setting the entry to undefined.

[ahejlsberg]

Not a fan of the ? and : prefix style. Would prefer to keep the existing formatting.

[rbuckton]

I can change it back. I primarily made the change to work around an issue with our .tmLanguage syntax coloring as the existing formatting resulted in syntax coloring being disabled/incorrect for the next 30 lines or so in VS Code.

[bterlson]

Both are nigh impossible to parse for a human, fwiw :-P

[rbuckton]

@bterlson, so how's that pattern matching proposal coming along? :)

[ahejlsberg]

👍 Once comments are addressed.

Thanks for cleaning all of this up. Much nicer with these changes. Just confirming that we still use MapLike<T> for the compiler APIs so minimize breaking changes?

[rbuckton]

I left everything as MapLike<T> that was not marked /* @internal */, so there should be no breaking changes against our public API.