Policy Provider SDK docs are not discoverable

[jkodroff]

What happened?

The navigation tree does not have a node for the Pulumi Policy SDKs under "Languages and SDKs" (there should be one for Node and Python:

The Policy SDK is technically navigable from https://www.pulumi.com/docs/languages-sdks/javascript/:

Also worth noting that if you navigate to the SDK, you're in "no man's land" in the docs hierarchy (see breadcrumbs below):

If you click on "Docs" in the breadcrumbs, it takes you to https://www.pulumi.com/docs/ which also does not exist anywhere in the nav tree.

Suggested fixes (TS shown, but would also apply to other languages especially Python which has multiple SDKs):

• Disambiguate the navigation link and all other references for the (IaC) SDK @pulumi/pulumi, e.g. "Pulumi Node SDK", "Pulumi Node SDK Reference", or "Pulumi IaC Node SDK/Reference" (if it aligns with our marketing, and there could be a conceivable ESC SDK), but not "SDK Docs" <-- Leaving this alone
• Add similar navigation nodes for the "Pulumi Policy SDK" @pulumi/policy
• Do the same for @pulumi/terraform unless this package has been moved to the registry. (It's currently not there because it's not schematized.) See: Schematize the pulumi-terraform provider pulumi-terraform#702 <-- It was moved to the registry
• Do the same for @pulumi/cloud (or remove it since it seems to be pretty inactive). <-- This is gone now.