[Feature Request] Add "Last Used" column to custom internal integration auth tokens

### Problem Statement

The customer was reviewing the custom internal integration settings and noticed that while it is currently visible when a token was created, they cannot find any information about when the token was last used.

### Solution Brainstorm

They would like to suggest adding an additional column to this page that displays the "Last Used" timestamp for each token. This would provide a quick and easy way for security personnel and administrators to monitor token usage.

### Product Area

Settings - Integrations

Start from Settings - Integrations and trace how custom internal integration auth tokens are stored, used, and displayed. Determine how a last-used timestamp can be surfaced in the token table, then verify that the column shows accurate usage information for existing and newly used tokens.

Written by the indexing model from the issue text.