chore(circuits): cleanup in kernel circuits and tests

[dbanks12]

Description

• Use builder assertions instead of ASSERT
• Add a missing read request tests to initial kernel tests
  • They already exist for inner kernel tests here, so they are mostly copy-pasted

Checklist:

• I have reviewed my diff in github, line by line.
• Every change is related to the PR description.
• I have linked this pull request to the issue(s) that it resolves.
• There are no unexpected formatting changes, superfluous debug logs, or commented-out code.
• The branch has been merged or rebased against the head of its merge target.
• I'm happy for the PR to be merged at the reviewer's next convenience.

[ludamad]

LGTM. I would almost think the error messages are too verbose, but I know all too well how needed that stuff is now :D