Fix STS SessionToken generation

[Neon-White]

Explain the changes

1. This PR fixes STS functionality by separating jwt_utils.make_auth_token into two functions - make_auth_token which always signs the request, and make_internal_auth_token that's used for RPC calls and only falls back to make_auth_token in case NOOBAA_AUTH_TOKEN isn't provided. Now, STS requests use make_auth_token directly, while internal callers were changed to use make_internal_auth_token

Issues: Fixed #xxx / Gap #xxx

1. https://bugzilla.redhat.com/show_bug.cgi?id=2009627

Testing Instructions:

1. See the following comment

• Doc added/updated
• Tests added

[guymguym]

I prefer to separate it to two different functions, one for simply make_auth_token that is simply signing the input, and a separate one to be used for rpc tokens which can be called make_internal_auth_token than can check the config for remote endpoints and if not then fallback to call the other function. This means replacing the callers to use the right variant, which will make it more explicit and safer

[shirady]

@Neon-White I deleted my comment because after sending it I saw @guymguym's comment.

[Neon-White]

Please note that I use Github's Squash and merge feature which merges a single squashed commit without modifying the branch - so the number next to Commits on top will remain 2, but the merge is squashed.

[Neon-White]

Squashed and merged