Consider writing an analyzer that produces warnings when using sync APIs on IDistributedCache

`IDistributedCache` has a few synchronous APIs

* https://docs.microsoft.com/dotnet/api/microsoft.extensions.caching.distributed.idistributedcache.get?#Microsoft_Extensions_Caching_Distributed_IDistributedCache_Get_System_String_
* https://docs.microsoft.com/en-us/dotnet/api/microsoft.extensions.caching.distributed.idistributedcache.refresh
* https://docs.microsoft.com/en-us/dotnet/api/microsoft.extensions.caching.distributed.idistributedcache.remove
* https://docs.microsoft.com/en-us/dotnet/api/microsoft.extensions.caching.distributed.idistributedcache.set

In the SqlServer and RedisCache implementations this ends up making blocking calls: e.g. https://github.com/dotnet/aspnetcore/blob/main/src/Caching/SqlServer/src/DatabaseOperations.cs#L54-L62. The proposal is to add an analyzer that warns against the use of these APIs.