[DocDB] Add support for Google tcmalloc

[amitanandaiyer]

Jira Link: DB-3241

Description

gperftools has a max-cap of 1G for thread cache max bytes.

This can be much lower than what we'd like to set it as for high memory machines. TCMalloc's latest code https://github.com/google/tcmalloc doesn't have this limitation and has other desirable properties such as per-core caching. We should consider moving to this version instead.