fix(Zero): Move Zero within Alpha

[manishrjain]

• Running Zero as a separate process makes deployments harder. A minimum cluster requires running both Zero process and Alpha process. In this PR, we remove the separate Zero process.
• Zero is now run as a module within Alpha. Every Alpha runs a Zero module (via goroutines, not a separate child process). Thus, all machines in the cluster participate in running a Zero Raft state machine.
• Alpha and Zero share the same Grpc Raft server. Messages to their Raft state machine are multiplexed using their Raft Context.
• Zero does not expose any user facing APIs. All user interactions are done via Alpha.
• This is a major simplification of the interactions between Zeros and Alphas.

Others:

• Simplified MembershipState.
• Consolidated all data directories under "data".
• Don't fork Lambda processes by default.

Removals:

• Zero process.
• Bulk loader is disabled for now as well.

---

This change is