[Makefile] Load Test Helpers for the poral

[Olshansk]

WIP

[commoddity]

The main issue here is that in local load testing PATH has no concept of a "Portal App ID" so this target doesn't really make sense.

For testing against production the concept is valid however.

This could, of course, change if/when we update the load tests to run against PATH + GUARD locally, but even then the default GUARD configuration uses only Envoy's API key auth, not our custom Grove-legacy Portal App ID/Secret Key auth.

In order for Portal App ID to make sense for local testing we would need to update:

1. Load tests to run against PATH + GUARD (currently they just run against a local PATH binary with no auth)
2. GUARD to run with Grove-legacy auth (PEAS, GUARD chart set to use Grove auth) (currently GUARD uses Envoy API key auth by default, not Grove-legacy auth)

[Olshansk]

The new docs make this quite easy.