[12.x] Cache isSoftDeletable(), isPrunable(), and isMassPrunable() directly in model

[shaedrich]

Classes rarely change at runtime, however, checking their dependencies every time we need them—sometimes even recursively—can be expensive. So, caching them makes sense.

Follow-up to #56060

as suggested in #56069 (comment)

[shaedrich]

I'm not quite sure why the tests fail all with a sudden despite not much being changed 🤔

[axlon]

@shaedrich not sure if this is why the tests are failing, but this doesn't work. All models will now share the same cache:

class ModelA extends Model
{
    use SoftDeletes;
}

class ModelB extends Model
{
}

dump(
    ModelA::isSoftDeletable(),
    ModelB::isSoftDeletable(),
);

// prints: true true

[shaedrich]

@axlon Right 😲 Thanks for pointing that out 👍🏻

I added a fix via efffda0 ✅