[Identity] Change default port to 50054 to avoid port collision
Summary:
Avoid future port testing or deployment conflicts
by defaulting port something other than default grpc port.
https://linear.app/comm/issue/ENG-3289
Test Plan:
Run identity service, keyserver, and native yarn dev
Create new user. Verify identity service is responding.
Reviewers: varun, bartek
Reviewed By: varun, bartek
Subscribers: ashoat, tomek, atul
Differential Revision: https://phab.comm.dev/D7028