[internal] refactor and minor improviment

**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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**Environment**
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**Error output**
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