[keyserver] Introduce yarn profile-prod to keyserver

Summary:
Introduce yarn profile-prod to keyserver which mirrors yarn prod (AKA will need to run yarn babel-build prior to running. Introducing yarn profile-dev is a bit more involved, and I'm not fully convinced is fully necessary.. but this works right now.

Depends on D9301

Test Plan:

1. yarn prod in web and landing
2. yarn babel-build && yarn profile-prod
3. CTRL-C to end profiling session
4. Here's the flamegraph:

Reviewers: ashoat, ginsu, tomek, rohan

Reviewed By: ashoat

Differential Revision: https://phab.comm.dev/D9302