VhdFileDirectory - improvements and fixes to Content files

[DmitryMashkov-DM]

Pull Request (PR) description

1. Added ContentEncoding property to properly support Content files (otherwise they are always written as Unicode) which corrupts some content types like UTF-8 XMLs.
2. Content files are not tested with ItemHasChanged (this didn't work anyway).
3. Fixed GetItemToCopy where an undefined DefaultValues array was used instead of DesiredProperties, resulting in a dead code, impacting properties like Force.
4. After #3 is fixed and the code is finally execuded, it would crash if a file is a Content (without SourcePath).
5. In SetVHDFile , Copy-Item's ErrorAction is set to Stop. Otherwise, the resource would simply ignore all errors and produce invalid configuration.

This Pull Request (PR) fixes the following issues

None

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This change is 

[codecov[bot]]

Codecov Report

Merging #179 into dev will decrease coverage by <1%. The diff coverage is 0%.

@@         Coverage Diff         @@
##            dev   #179   +/-   ##
===================================
- Coverage    73%    73%   -1%     
===================================
  Files        11     11           
  Lines      1401   1402    +1     
===================================
  Hits       1035   1035           
- Misses      366    367    +1

[aromano2]

Hi Dmitry, can you please open an issue for this feature so that we have more context? Also, could you add appropriate tests for the new functionality please? Thanks for the contribution!

[johlju]

We have renamed the resource, removing 'x', so please rebase this PR.