Simple payload generator section

How to run:

1. Setup postgres via make run_postgres, docker is required
2. Attach to database via make attach_postgres
3. Create metrics table: create table metrics(id bigserial, value text);
4. Run load: cargo run -- --batch-size 10000

How to build:

Assuming mac os:

1. run make cross_openssl
2. run make build_x64
3. scp final binary from target/x86../release/payload_gen to where it's needed