Fix using Definitions as arguments to Definitions (backport #3726)

[mergify]

This is an automatic backport of pull request #3726 done by Mergify.
Cherry-pick of a050b8c has failed:

On branch mergify/bp/3.6.x/pr-3726
Your branch is up to date with 'origin/3.6.x'.

You are currently cherry-picking commit a050b8cda.
  (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/experimental/hierarchy/DefinitionSpec.scala
	modified:   src/test/scala/chiselTests/experimental/hierarchy/Examples.scala

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   core/src/main/scala/chisel3/Module.scala
	both modified:   core/src/main/scala/chisel3/experimental/hierarchy/core/Definition.scala
	both modified:   core/src/main/scala/chisel3/experimental/hierarchy/core/Instance.scala
	both modified:   core/src/main/scala/chisel3/internal/Builder.scala
	both modified:   src/main/scala/chisel3/aop/injecting/InjectingAspect.scala
	both modified:   src/main/scala/chisel3/stage/phases/Elaborate.scala

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

---

Mergify commands and options

More conditions and actions can be found in the documentation.

You can also trigger Mergify actions by commenting on this pull request:

• @Mergifyio refresh will re-evaluate the rules
• @Mergifyio rebase will rebase this PR on its base branch
• @Mergifyio update will merge the base branch into this PR
• @Mergifyio backport <destination> will backport this PR on <destination> branch

Additionally, on Mergify dashboard you can:

• look at your merge queues
• generate the Mergify configuration with the config editor.

Finally, you can contact us on https://mergify.com

---

Original PR Body

Chisel creates new contexts whenever you're constructing a Definition. Previously, if you had a Definition in the parent context, the actual object would not be available in the child context (because it's a new context, Builder.components is cleared when you go to a new context). Now, we keep track of definitions explicitly including definitions from parent/outer scopes. This is implemented using a nested List for efficiency of constructing the datastructure while still allowing for efficient iteration.

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

• Performance improvement - but probably not measurable
• Bugfix

Desired Merge Strategy

• Squash

Release Notes

Fixes #3708

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: 3.5.x, 3.6.x, or 5.x depending on impact, API modification or big change: 6.0)?
• 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.