1.19.0-preview

This preview release contains a preview version of MSAL.NET, 4.37.0-preview, which includes token cache improvements. The .AddMemoryCache should now be much faster, but the memory is not bounded, nor does it have any eviction policies, so not recommended for use in production if user flows are involved (GetTokenForUser). Once MSAL.NET releases 4.37.0, Microsoft.Identity.Web will release an out of preview version as well.