ESC: Revise providers pages

[jkodroff]

For all of the https://www.pulumi.com/docs/esc/providers/ pages:

• Explain what the provider does
• Give a complete working example:
  • For OIDC, it should include outputs that map to provider config, if applicable. Prefer environment variables over pulumi config.
  • For dynamic secrets, it should include pulumi config outputs
• Put pulumi-stacks and terraform-state put them in a separate IaC category (alongside OIDC and Secrets & Config)
• Make the schema reference sections consistent:
  • The schema sections should be scannable in terms of their headers
  • If this can be done easier with an external data source or shortcode, let's do that

[jkodroff]

This was done in the ESC epic.