Get rid of or property-ify d.py-style `is_x` getters

[ToothyDev]

There are many places in pycord where seemingly unnecessary (boolean) getters exist, which only return the attribute in question. These are often also not properties. @vmphase compiled a list of places where such getters are used here

Question would be whether these getters are all made into properties, and / or where possible, gotten rid of altogether and replaced with direct attribute access

[vmphase]

In my opinion, the ones that are semantically just returning an attribute should simply be removed in favor of direct attribute access. For instance: is_nsfw() just returns self.nsfw, so it would be cleaner to have users access .nsfw directly. Furthermore, changing these to properties later will not be considered a breaking change.

Nevertheless, getters that perform additional logic (checks, guards, or otherwise derive a value rather than simply exposing an attribute) make more sense as properties.

[ToothyDev]

@Lulalaby @Paillat-dev wdyt?