feat(AzureEnvironments): use upstream func for validation

[JefeDavis]

What this PR does / why we need it

removes hard-coded maps for Azure environments and calls the EnvironmentFromName function from go-autorest/azure library to leverage upstream provider to validate Azure Environments. Also enables initial ability to specify custom endpoints for AzureStackCloud by using the Environment 'AzureStackCloud', specifying AZURE_ENVIRONMENT_FILEPATH, and providing an AzureEnvironment json file

Which issue(s) this PR fixes

Fixes #3162

Describe testing done for PR

Unit tests have been added to cover this change

Release note

Fixes validation handling when attempting to deploy to AzureStackCloud custom endpoints

Additional information

Special notes for your reviewer

[JefeDavis]

@mminges @conzetti

[github-actions[bot]]

Hi @JefeDavis! And thank you for opening your first Pull Request. Someone will review it soon. Thank you for committing to making Tanzu Framework better.