[PowerShell] Improve generated PowerShell examples

[SimeonGerginov]

1. Integer default value in the examples is changed from 123 and 789 to 0.
2. String default value is now constructed from the name of the parameter/property and the prefix My. Previously the suffix example was part of the value.
3. Enum examples are now generated using one of the allowed values of the Enum instead of using the Initialize-* cmdlets as before.
4. Arrays with one element result in the value directly instead of adding the @() syntax.
5. Maps are now fully supported using the hashtable syntax in PowerShell.
6. Models are extracted and generated in the correct order instead of nesting them on a single line when invoking the cmdlet.
7. The verb that is used in the examples for the Models cmdlets can now be specified through an additional property. The default value remains Initialize.
8. Classname is used instead of Name in the Models cmdlets initialization. This can be controlled through an additional boolean property which specifies whether to use Classname instead of Name.
9. The PowerShell Samples are updated to reflect the latest example structure.
10. The docs template for the APIs is modified as well to reflect the latest example structure.
11. The documentation for PowerShell is changed to reflect the new additional properties.

Closes #9826
@wing328

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• Run the following to build the project and update samples:

  ./mvnw clean package 
  ./bin/generate-samples.sh
  ./bin/utils/export_docs_generators.sh
  

  Commit all changed files.
  This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master.
  These must match the expectations made by your contribution.
  You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*.
  For Windows users, please run the script in Git BASH.
• File the PR against the correct branch: master, 5.1.x, 6.0.x
• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.

[wing328]

@SimeonGerginov thanks for the PR. I'll review tomorrow and merge if no question from me.

[wing328]

Merged into master and updated samples via 173c7ca