Rollup merge of #70712 - :stabilize-remove-entry, r=Amanieu
Rollup merge of #70712 - :stabilize-remove-entry, r=Amanieu

stabilize BTreeMap::remove_entry

This PR stabilizes `BTreeMap::remove_entry` as implemented in https://github.com/rust-lang/rust/pull/68378.

Closes https://github.com/rust-lang/rust/issues/66714

graydon/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust