Add support for `rustls-platform-verifier`

[manifest]

I have found these related issues/pull requests

The issue is related to #4033.

Description

Adding rustls-platform-verifier allows to use rustls with aws-lc-rs and platform's native CA certificates.

Prefered solution

Add new feature flags to enable platform's native CA certificates provided by rustls-platform-verifier.

Is this a breaking change? Why or why not?

No. This adds a new feature.