Improve assess and regression time

[celinval]

Description of changes:

The per-reachability analysis can cause a big penalty when assessing a project that has lots of tests.

Change that for now.

Despite that improvement, assessing the firecracker still takes a long time, even with --only-codegen, due to the number of calls done to goto-cc. Thus, don't use assess here.

Resolved issues:

N/A

Related RFC:

Optional #ISSUE-NUMBER.

Call-outs:

Due to #2472, we need a specialized name for each test harness. For now, we just replicate the model for each harness.

Testing:

• How is this change tested?

• Is this a refactor change?

Checklist

• Each commit message has a non-empty body, explaining why the change was made
• Methods or procedures are documented
• Regression or unit tests are included, or existing tests cover the modified code
• My PR is restricted to a single feature or bugfix

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