Add support for OneBox Environment, Fixes AB#3113751

[shahzaibj]

Fixes AB#3113751

Changes to allow MSAL/Broker to talk to eSTS running locally. This basically does the following:

• Add build config flag to bypass authority validation. This is required because local eSTS authorities are not discovered via cloud discovery. We can enable this flag locally in gradle project properties to target local eSTS.
• Read the port number of the authority when constructing the cloud URL because targeting local eSTS requires supplying exact port. I've scoped the change to read port only when environment is specified as onebox.

Related MSAL PR: AzureAD/microsoft-authentication-library-for-android#2231

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