add selectors and azclient cleanup

[davidgamero]

Description

Changes in setup-gh command:

• Centralize Credentials management in AzClient
• Abstract AzClient out of the SetupCommand
• Provide a default app name of "-workflow"
• Use the Select Prompt for Tenant and ResourceGroup
• Autofill gh repo name default value using gh cli
• Allow overriding validators (gh repo/az cli validity checks)
• Update Select Searcher to allow matching out-of-order terms (space delimited, case-insensitive)

[Tatsinnit]

❤️ Looks good to me, thank you so much for this, I've added folks who have touched this in past just as eyeball and I am sure you have taken care of the rest!! Thank you for the ping as well.

[Tatsinnit]

☕️❤️

[bfoley13]

will be nice to have this in!