[dv] Decouple regression reporting from regression runs.

### Description

This issue tracks the request to decouple the nightly regression reporting infrastructure from the block and top level regression runs.

This will give us the ability to parallelize the block level regressions as separate dvsim invocations, and get to an 8h or less turnaround time (ignoring top level tests).

The publishing step should have two main flows:

1. Command to handle block or top level submission.
2. Command to refresh the overall regression report.

The overall regression table may need to start displaying the commit hash for each IP block.

The issue names no files or tests; begin by tracing the nightly regression reporting infrastructure and the dvsim submission and publishing entry points. Confirm the two requested flows—block or top-level submission and overall report refresh—and the requirement to show each IP block's commit hash.

Written by the indexing model from the issue text.