Auto merge of #132597 - lukas-code:btree-plug-leak, r=jhpratt

btree: don't leak value if destructor of key panics

This PR fixes a regression from rust-lang/rust#84904.

The `BTreeMap` already attempts to handle panicking destructors of the key-value pairs by continuing to execute the remaining destructors after one destructor panicked. However, after #84904 the destructor of a value in a key-value pair gets skipped if the destructor of the key panics, only continuing with the next key-value pair. This PR reverts to the behavior before #84904 to also drop the corresponding value if the destructor of a key panics.

This avoids potential memory leaks and can fix the soundness of programs that rely on the destructors being executed (even though this should not be relied upon, because the std collections currently do not guarantee that the remaining elements are dropped after a panic in a destructor).

cc `@Amanieu` because you had opinions on panicking destructors

Author: bors