Fix boring tap of non-passive source from parent. (backport #4083)

[mergify]

Expected result is fully aligned, which is what happens when reading from a probe.

When the source is already at the LCA (from parent) there's no probe and the secret connections only support a few commands.

For lack of a way to do, e.g., :#= here,
use read(probe(x)) to get the fully aligned result that's expected and bored down to the child.

This isn't ideal but fixes this using only the sorts of expressions and commands that we've already committed to supporting.

Fixes #3557.

Contributor Checklist

• Did you add Scaladoc to every public function/method?
• Did you add at least one test demonstrating the PR?
• Did you delete any extraneous printlns/debugging code?
• Did you specify the type of improvement?
• Did you add appropriate documentation in docs/src?
• Did you request a desired merge strategy?
• Did you add text to be included in the Release Notes for this change?

Type of Improvement

• Bugfix

Desired Merge Strategy

• Squash: The PR will be squashed and merged (choose this if you have no preference).

Release Notes

Fix tapping mix-alignment signal from parent.

Reviewer Checklist (only modified by reviewer)

• Did you add the appropriate labels? (Select the most appropriate one based on the "Type of Improvement")
• Did you mark the proper milestone (Bug fix: 3.6.x, 5.x, or 6.x depending on impact, API modification or big change: 7.0)?
• Did you review?
• Did you check whether all relevant Contributor checkboxes have been checked?
• Did you do one of the following when ready to merge:
  • Squash: You/ the contributor Enable auto-merge (squash), clean up the commit message, and label with Please Merge.
  • Merge: Ensure that contributor has cleaned up their commit history, then merge with Create a merge commit.

---

This is an automatic backport of pull request #4083 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 0dbedc3 has failed:

On branch mergify/bp/6.x/pr-4083
Your branch is up to date with 'origin/6.x'.

You are currently cherry-picking commit 0dbedc315.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   src/test/scala/chiselTests/BoringUtilsTapSpec.scala

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   core/src/main/scala/chisel3/RawModule.scala

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[jackkoenig]

I intentionally rebased this on top of 1 commit older of 6.x (i.e. not tip of 6.x) because I'm trying to trigger the issue where Mergify will attempt to update the branch by merging 6.x and then EasyCLA will block the PR because mergify[bot] hasn't signed the CLA. I'm going to send this branch to EasyCLA Support to see if they can help get it to just ignore mergify[bot]! Please don't Update branch nor rebase to get this merged [yet] 🙂

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: jackkoenig / name: Jack Koenig (9f8287a)
• ✅ login: dtzSiFive / name: Will Dietz (afd7bfc)

[jarias-lfx]

/easycla