AzureDevOpsDsc: Increase Azure DevOps API timeout and other minor fixes (fixes #5, #10, #11, #12 and #25)

[SphenicPaul]

Pull Request (PR) description

Includes a number of minor fixes to close some small/minor issues:

• Increased the default, Azure DevOps API, timeout returned by Get-AzDevOpsApiWaitTimeoutMs to 300000 (5 minutes). Also increased related, parameter validation ranges within Test-AzDevOpsApiTimeoutExceeded, Wait-AzDevOpsApiResource and Wait-AzDevOpsApiOperation functions (fixes #25).
• Updated contextual help (fixes #5).
• Removed the Classes and Examples directories from the build.yaml so they don't get copied into the module output (fixes #10 and #11).
• Moved 'Ensure' and 'RequiredAction' enums into 'Enum' directory and out of 'prefix.ps1' (fixes #12)

This Pull Request (PR) fixes the following issues

• Fixes #5
• Fixes #10
• Fixes #11
• Fixes #12
• Fixes #25

Task list

• [x] 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.
• [x] Code changes adheres to DSC Community Style Guidelines.

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This change is 

[SphenicPaul]

@johlju - Shout if you've any questions with this. Nothing too major within these changes.

The integration tests ran OK locally against my Azure DevOps instance so I'd expect them to run OK when merged. Additionally, the API timeout is now 5 minutes so that should resolve the intermittent, integration failures.

I might look at the SQL Server (2019) and Azure DevOps Server (2020) installs (on build server as part of integration tests) for the next PR.