feat: added warnings for certain events that require an intent

[Jaskowicz1]

This PR adds warnings for some events (guild member events and presence update) if the user does not have the specific intent required.

As these events do not fire from Discord if the intent wasn't specified, I could not use the set_warning_callback feature.

This is to try and inform users about what went wrong and how they can fix it, to try be more user friendly as D++ is currently silent about it (see link a and link b).

Code change checklist

• [x] I have ensured that all methods and functions are fully documented using doxygen style comments.
• [x] My code follows the coding style guide.
• [x] I tested that my change works before raising the PR.
• [x] I have ensured that I did not break any existing API calls.
• [x] I have not built my pull request using AI, a static analysis tool or similar without any human oversight.

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[Jaskowicz1]

what about if the user hooks the event after starting the cluster?

Couldn't come up with a solution to that, that didn't involve constantly checking every second if the events have been bound to, when I was writing this (and I still don't have a solution).

also, while looking at this do we make the one for messages less spammy too? basically make them all emit once?

Either that or add something like bot.suppress_warnings(true); to prevent warning logs for this (for people who do know what they're doing)? I think being spammy drills in the idea that they're doing something wrong to people who might not understand.