Import-SqlDscPreferredModule: Add new command

[johlju]

Pull Request (PR) description

• SqlServerDsc
  • The following public functions were added to the module (see comment-based
    help for more information):
    • Import-SqlDscPreferredModule
  • The module will now call Import-SqlDscPreferredModule when the module
    is imported to make sure SqlServer (default preferred module) or SQLPS
    is loaded into the session. This will make it possible for classes and
    commands to use and return SQL types. If no module is found it will
    output a warning to install any of the dependent modules.
• SqlServerDsc.Common
  • Import-SQLPSModule
    • The function was changed to call public command Import-SqlDscPreferredModule.

This Pull Request (PR) fixes the following issues

Closes #654

Task list

• Added an entry to the change log under the Unreleased section of the
  file CHANGELOG.md. Entry should say what was changed and how that
  affects users (if applicable), and reference the issue being resolved
  (if applicable).
• Resource documentation updated in the resource's README.md.
• Resource parameter descriptions updated in schema.mof.
• Comment-based help updated, including parameter descriptions.
• Localization strings updated.
• Examples updated.
• Unit tests updated. See DSC Community Testing Guidelines.
• Integration tests updated (where possible). See DSC Community Testing Guidelines.
• Code changes adheres to DSC Community Style Guidelines.

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This change is 

[codecov]

Codecov Report

Merging #1846 (1438c1c) into main (3a46100) will decrease coverage by 1%.
The diff coverage is 95%.

@@         Coverage Diff          @@
##           main   #1846   +/-   ##
====================================
- Coverage    91%     91%   -1%     
====================================
  Files        71      73    +2     
  Lines      7363    7366    +3     
====================================
+ Hits       6715    6716    +1     
- Misses      648     650    +2     

Flag	Coverage Δ
unit	91% <95%> (-1%)	⬇️

Impacted Files	Coverage Δ
source/suffix.ps1	33% <33%> (ø)
...dules/SqlServerDsc.Common/SqlServerDsc.Common.psm1	98% <100%> (-1%)	⬇️
source/Public/Import-SqlDscPreferredModule.ps1	100% <100%> (ø)

[johlju]

Reviewed 75 of 78 files at r1, 6 of 6 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @johlju)