Deprecate calling .viewAs on non-hardware (backport #3395)

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This is an automatic backport of pull request #3395 done by Mergify.
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	modified:   core/src/main/scala/chisel3/experimental/dataview/package.scala
	modified:   core/src/main/scala/chisel3/internal/Builder.scala

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	both modified:   src/test/scala/chiselTests/experimental/DataView.scala

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Original PR Body

It's an error in most cases already, and in the cases it isn't, make it a warning. Also fix a crash that could occur when viewing a non-Data containing non-hardware Data.

I will immediately follow this PR with one turning it into an error, but I want to fix the crash in Chisel 5 and 3.6 because the errors are super opaque.

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

• API deprecation

Desired Merge Strategy

• Squash

Release Notes

Also fix a crash that could occur when viewing a non-Data containing non-hardware Data.

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 or 3.6.x depending on impact, API modification or big change: 5.0.0)?
• 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.