Entra ID integration: add onboarding script

[justinas]

Adds a new teleport integration configure subcommand to set up Azure OIDC integration. The command sets up:

• An Entra ID enterprise application, both as an SSO connector to allow login with Entra to Teleport, and as a way for us to access Entra ID directory programatically (via OIDC auth).
• Optionally, when access graph support is requested, queries information about existing enterprise applications from the "private" Azure API (see RFD for more info) and produces a JSON payload that the user is expected to upload when finishing the integration onboarding in the UI.

Also adds the web endpoint in the Proxy that generates the script wrapper for this.

Still missing:

• Frontend to onboard Entra that utilizes this. Will come as a subsequent PR.