[Feature]: Volume discount stats API should show volume even if below tier 1

[JonRay15]

Feature Overview

Currently the volumeDiscountStats API will only show a record for a party if it has reached enough running volume to qualify for tier 1.

This means that anyone trading some volume who wants to know how close they are to reaching that first tier does not get any useful feedback.

Tasks

A checklist of the tasks that are needed to develop the feature and meet the acceptance criteria and feature test scenarios.

• Enhance the API to emit an event every epoch even if the party is not in tier 1 or above

Feature test scenarios

Detailed scenarios that can be executed as feature tests to verify that the feature has been implemented as expected.

GIVEN party has some volume but not enough for tier 1
WHEN at the end of the epoch
THEN the API shows the running volume and the fact no discount has been granted

Additional Details (optional)

Any additional information that provides context or gives information that will help us develop the feature.

Small change to Console to make this easier to understand until this is delivered: vegaprotocol/frontend-monorepo#5447