Revert jemalloc upgrade in 10.6
This is the action item we have to resolve the issues with jemalloc crashing ruby by reverting the jemalloc upgrade:
#3083 (closed) #3313 (closed) #3329 (closed)
An upstream issue has been logged here: https://github.com/jemalloc/jemalloc/issues/1150
and the following two upstream issues may be related:
https://github.com/jemalloc/jemalloc/issues/1006 https://sourceware.org/bugzilla/show_bug.cgi?id=11787
There is also a ruby commit in 2.5.0 that may resolve the issue, that we can explore potentially backporting in a followup https://github.com/ruby/ruby/commit/410362f6a25f561a8cb9f6aeba34efd3125371a5