[Feature Request]: Add aggregated metrics view for transforms running with multiple copies

### What would you like to happen?

Description:
Currently, when a transform runs with multiple copies, metrics are displayed separately for each copy. This makes it harder to quickly understand the total execution result of the transform and sometimes forces users to create artificial workarounds, such as adding a Dummy transform only to consolidate the final count.

The proposal is to improve the metrics view for transforms with multiple copies by displaying a single aggregated row first, with the option to expand it and inspect the metrics of each individual copy.

Objective:
Make operational analysis easier and remove the need for helper transforms used only to obtain a consolidated execution view.

Expected behavior:

when a transform has multiple copies, show a main row with the aggregated total;
provide an expand icon, such as an arrow, to reveal per-copy details;
keep the individual metrics for each copy available;
apply aggregation to the main metrics, such as rows read, written, rejected, errors, and other relevant counters;
preserve the current detailed view as the expanded mode, without losing information.

Benefits:

faster metrics reading;
better usability for parallelized pipelines;
reduced visual complexity;
no need to use a Dummy transform only to get totals;
improved monitoring and troubleshooting experience.

Desired example:
Current:

Rest Total (copy 0)
Rest Total (copy 1)
Rest Total (copy 2)
Rest Total (copy 3)

Proposed:

Rest Total [aggregated total]
copy 0
copy 1
copy 2
copy 3

Note:
The goal is not to remove per-copy detail, but to present a consolidated view first, with an option to expand.

### Issue Priority

Priority: 3

### Issue Component

Component: Hop Gui

Start in the Hop Gui metrics view and trace how metrics for transform copies are currently presented. Identify the existing aggregation data and expand/collapse entry points, then verify that the main row shows totals while the expanded view retains each copy's metrics.

Written by the indexing model from the issue text.