[internal] refactor and minor improviment

[VeryEarly]

Component

[x] PowerShell module
[] VSCode extension
[] Other

Description of the issue
minor issues and refactor needed:

• hide unused cmdlets: Get-AzUpgradeCmdletSpec, Get-AzUpgradeAliasSpec to private
• refine parameters of existing cmdlets (need to discuss)
• refactor Disable/Enable AzUpgradeDataCollection

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[isra-fel]

hide unused cmdlets: Get-AzUpgradeCmdletSpec, Get-AzUpgradeAliasSpec to private
-> this would be breaking change. we need to check the usage.

TODO: create ADO