De-emphasize Aws native in docs

A few changes to docs to avoid steering people to using aws-native that don't have a good reason to:

Remove the "Classic" branding from the pulumi-aws provider in docs
Demote AWS Native provider on the AWS & Pulumi | Pulumi Docs page.
Use azure-native rather than aws-native in a few places where we're just giving an example of a native provider

I left all the blog posts using aws-native untouched; there's nothing wrong with having this content despite the fact that we're no longer trying to promote aws-native as much.

Part of the work towards: https://github.com/pulumi/pulumi-aws-native/issues/1698 and https://github.com/pulumi/pulumi-aws-native/issues/1697 (remainder needs to be done in the registry)

pulumi / docs

De-emphasize Aws native in docs #12892