Update CoreAdminSecurityOptions.cs to support setting more than just IgnoreEntityTypes

[devantler]

Removed "internal set" as this restricts us from initializing anything other than the IgnoreEntityTypes.

I need to do this which was not possible:

services.AddCoreAdmin(new CoreAdminOptions()
{
    RestrictToRoles = "Admin"
    IgnoreEntityTypes = new List<Type>() { typeof(PersistedGrant), typeof(DeviceFlowCodes) }
});