[Feature Request] Optimize OIDC and instance discovery calls

[bgavrilMS]

High scale, multi-tenant applications should not have to perform too many discovery calls, as this affects their performance.

OIDC Discovery

MSALs have no need for OIDC discovery from AAD (and even ADFS) authorities. Instead, MSAL can pre-compute the token and authorization endpoints.

Instance discovery

There are several optimizations that can be done here, see full spec here

The simplest is add a simple static cache between HOSTNAME and instance discovery result

instance_discovery_cache [ "login.microsoft.com"] = JSON

This will solve most problems, except for command line apps performing instance discovery on each call to GetAccounts / AcquireTokenSilent. If needed to implement, please track separately. WAM should not require this.