Rollup merge of #28988 - ahmedcharles:liballoc_jemalloc, r=nrc
Rollup merge of #28988 - ahmedcharles:liballoc_jemalloc, r=nrc


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