Rollup merge of #43125 - aochagavia:stable_drop, r=arielb1
Rollup merge of #43125 - aochagavia:stable_drop, r=arielb1

Add regression tests to ensure stable drop order

Work towards #43034

I think this is all we need to do on the testing front regarding RFC 1857

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