ADUser: Uses helper function Add-TypeAssembly

[johlju]

Pull Request (PR) description

• Changes to ADUser
  • Now uses the helper function Add-TypeAssembly which have some benefit
    instead of directly using Add-Type, like verbose logging (issue ADUser: Use helper function Add-TypeAssembly #431).

This Pull Request (PR) fixes the following issues

• Fixes ADUser: Use helper function Add-TypeAssembly #431

Task list

• Added an entry under the Unreleased section in the CHANGELOG.md.
  Entry should say what was changed, and how that affects users (if applicable).
• Resource documentation added/updated in resource directory README.md.
• Resource parameter descriptions added/updated in schema.mof
  and comment-based help.
• Comment-based help added/updated.
• Localization strings added/updated in all localization files as appropriate.
• Examples appropriately added/updated.
• Unit tests added/updated. See DSC Resource Testing Guidelines.
• Integration tests added/updated (where possible). See DSC Resource Testing Guidelines.
• New/changed code adheres to DSC Resource Style Guidelines and Best Practices.

---

This change is 

[codecov-io]

Codecov Report

Merging #458 into dev will decrease coverage by <1%.
The diff coverage is 0%.

@@         Coverage Diff         @@
##            dev   #458   +/-   ##
===================================
- Coverage    98%    98%   -1%     
===================================
  Files        20     20           
  Lines      2815   2816    +1     
  Branches     10     10           
===================================
  Hits       2767   2767           
- Misses       38     39    +1     
  Partials     10     10

[johlju]

Reviewed 2 of 2 files at r1.
Reviewable status: complete! all files reviewed, all discussions resolved