`Bucket::drop` and `Bucket::read` need to be used with deprecated `RawTable::erase_no_drop`

[JustForFun88]

I'm trying to document a raw part of the crate and was thinking about the safety concerns of the Bucket<T> methods, but I suddenly realized that the two public methods, Bucket::drop and Bucket::read, potentially lead to double-drop in RawTable, since they cannot be used without RawTable::erase_no_drop but this method has been deprecated since version "0.8.1".

So we need to come up with something:

• make Bucket::drop and Bucket::read deprecated too;
• make RawTable::erase_no_drop not a deprecated method;
• separately document these potential double-drop for Bucket::drop and Bucket::read methods? But it is not clear how to document this for Bucket::drop, the Bucket::read method can at least be used in conjunction with core::mem::forget.

[Amanieu]

I thought about this for a bit and I think the best solution is to deprecate drop, read as well and point people to use remove and erase on RawTable instead.

[Amanieu]

Actually we can remove the deprecated methods since the next version of hashbrown will be a major version bump.