Client: Only allow pointing with interact priv

[appgurueu]

Trivial UX improvement: When you don't have interact, you can't point at anything anymore, to signal that you are unable to interact with anything.

Previously, client prediction made it look as if you were still able to interact with things, even though the server ignores the interactions. You could still point at things, "dig" nodes (clientside), "punch" and "kill" entities clientside.

Provides a solution for part of the use case behind #14742: Simply revoking interact should now work well. Care needs to be taken to re-grant interact on player join, since privs are persisted.

The use case of tools that can't point at anything is however still valid, but a bit trickier to solve.

If we were to change behavior and make range = 0 => no pointing, the fix would be trivial: Add d > 0 && to the condition. (Oh also, it looks like you can still point at nodes you are inside of when you are in third person?)

(However, with a negative range or similar, it's a bit trickier: We already use a negative value (-1) as the default for "no value". This was what led me down the route of NaN back then, which in hindsight was a bad idea.)

How to test

1. Host server
2. Join with second client (can't revoke interact from singleplayer / admin)
3. Revoke interact priv of second client
4. Notice that second client can't point at anything anymore

[cx384]

I like the idea, but I'm not so sure if we really want this.
For example, if a server requires new players to read rules before they can get interact, and if the rules are written down on signs using infotext, new players can't read them anymore. (The rules contain a hidden password/command to grant them interact.) There were/are definitely servers which do this, so this change may break something.

Also, regarding further client side modding, it may problematic if players need interact to point something.
(A similar problem occurs when you prohibit pointing of unauthorized players in protected areas.)

[appgurueu]

You're right, this would be a breaking change. I hadn't thought about e.g. infotext. Thanks for pointing this out.