Non-idempotent names in BoringUtils() break chisel-testers2 caching

[oharboe]

Type of issue: bug report

Other information

Tests run in parallel will not have predictable names from BoringUtils.bore() as the name picked for the signal is based on an increasing counter shared across threads.

If the current behavior is a bug, please provide the steps to reproduce the problem:

What is the current behavior?

BoringUtils.bore() names can vary in tests depending on whether they are run in serial or in parallel.

What is the expected behavior?

BoringUtils.bore() should be idempotent: it shouldn't matter how you invoke the tests.

Please tell us about your environment:

v3.5.0-RC2

What is the use case for changing the behavior?

Caching should work when running tests in parallel.