Azure Region not prepended to the endpoint while using ESTS-R with Microsoft.Identity.Web 1.19.0

[sangs-msft]

Which version of Microsoft Identity Web are you using?
E.g. Microsoft Identity Web 1.19.0

Where is the issue?

• Web app
  • Sign-in users
  • Sign-in users and call web APIs
• Web API
  • Protected web APIs (validating tokens)
  • Protected web APIs (validating scopes)
  • Protected web APIs call downstream web APIs
• Token cache serialization
  • In-memory caches
  • Session caches
  • Distributed caches
• Other (please describe)

Is this a new or an existing app?
a. The app is in production using the old version and I have upgraded to a new version of Microsoft Identity Web to incorporate ESTS-R changes

Repro
In order to repo, use the code snippet mentioned here https://identitydocs.azurewebsites.net/static/v2/msal-net-regional-adoption.html#providing-a-region-with-microsoftidentityweb to enable ESTS-R

      services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
          .AddMicrosoftIdentityWebApi(
              configureJwtBearerOptions: jwtOptions => { },
              configureMicrosoftIdentityOptions: msIdentityOptions =>
              {
                  msIdentityOptions.Instance = options.AuthenticationEndpoint.AbsoluteUri;
                  msIdentityOptions.TenantId = options.DefaultTenantId;
                  msIdentityOptions.SendX5C = true;
                  msIdentityOptions.ClientId = options.ClientApplicationId;
                  msIdentityOptions.ClientCertificates = new[]
                  {
                      CertificateDescription.FromStoreWithDistinguishedName(options.ClientCertificateSubjectName, StoreLocation.LocalMachine, StoreName.My),
                  };
              })
          .EnableTokenAcquisitionToCallDownstreamApi(configureConfidentialClientApplicationOptions: clientAppOptions => { })
          .AddInMemoryTokenCaches();
      services.Configure<ConfidentialClientApplicationOptions>(
          JwtBearerDefaults.AuthenticationScheme,
          applicationOptions => { applicationOptions.AzureRegion = options.Region; });

**Expected behavior**
It is expected that we hit the regional endpoint to acquire token. 
Ex - https://centraluseuap.login.microsoft.com

**Actual behavior**
We are hitting the global endpoint in spite of enabling ESTS-R 
https://login.microsoft.com


**Additional context / logs / screenshots / link to code**
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Add any other context about the problem here, such as logs and screenshots, or even links to code.

[jennyf19]

Included in 1.21.0 release