Replace outdated jemalloc #4766
Description
We are currently using https://github.com/gnzlbg/jemallocator. We should switch to https://github.com/tikv/jemallocator.
See rust-lang/rust#83152 for context.
My TL;DR: first crate uses old jemalloc, and it doesn't set it up to use the most efficient APIs. tikv fork fixes both problems, and delivers a sizable performance increase. I've just re-checked it, and for one rust-analyzer this yields 5% decrease in the number of executed instructions.