More tests in nightly regression

Placeholder David Harris
2025-05-13T08:13:14Z

Performance validation: CoreMark, Embench, cache, branch, ways to detect issues
Tests with multiple simulators
Lockstep tests
Code coverage
Functional coverage

Some of this depends on having a single test bench that supports lockstep, and replacing run-elf / run-elf-cov, iter-elf.

Update testplan.md when done