Show timestamps in "Manage logs and telemetry" on dashboard

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Is your feature request related to a problem? Please describe the problem.

I run the Aspire dashboard standalone and intermittently export telemetry to it from service instances that have the same `service.name` but different random `service.instance.id`. Then, I want to delete the data of older resources from the dashboard and keep only the newest. I open the dashboard settings and click the "Manage" button, which opens "Manage logs and telemetry". That shows a list of service names and instance IDs with checkboxes, but it is difficult for me to recognize which of those is the newest one.

### Describe the solution you'd like

In the "Manage logs and telemetry" dialog box, show also the timestamp of the latest telemetry signal of each resource, in a new column between "Name" and "Summary". Combine all types of signals (structured logs, traces, and metrics). For this purpose, I'd prefer absolute timestamps rather than relative.

In that dialog box, there is an expander button at the left side of each per-resource check box. When clicked, that opens a list of signal types for that resource. It would be possible to show the earliest and latest timestamp for each signal type there, but that is not necessary for my purposes.

### Additional context

_No response_