Don't prefix package name in _types package in VHDL (copy #1997)

[mergify]

This is an automatic copy of pull request #1997 done by Mergify.
Cherry-pick of 5c6bf8b has failed:

On branch mergify/copy/1.2/pr-1997
Your branch is up to date with 'origin/1.2'.

You are currently cherry-picking commit 5c6bf8b0b.
  (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:
	new file:   changelog/2021-11-11T11_29_26+01_00_unqualify_package_body_vhdl.md
	new file:   tests/shouldwork/Issues/T1996.hs

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	both modified:   clash-lib/src/Clash/Backend/VHDL.hs
	deleted by us:   tests/Main.hs

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

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[alex-mckenna]

Pipelines don't report correctly on 1.2 anymore, but this succeeded on this pipeline: https://gitlab.com/clash-lang/clash-compiler/-/pipelines/407861240