Enable --strictPropertyInitialization for library code

[jelbourn]

We want to turn this on so that cdk/material don't have an exception inside Google (which has all strictness checks enabled).

[rkirov]

Ping on this, looks like there are still some failures. I can blast ! with an autofixer if you will prefer that?

[jelbourn]

@rkirov Kristiyan had a PR, but we deprioritized it over other stuff. How aggressively do you want to turn off this exception?

[rkirov]

It is not urgent, we were just cleaning up the special exceptions for not particular reason. We can wait another year.