updated LazyResolverMixin.GetOrResolve to be thread safe using lock and rechecking for entry before inserting into cache
updated LazyResolverMixin.GetOrResolve to be thread safe using lock and rechecking for entry before inserting into cache

thenerdery/UmbracoVault,thenerdery/UmbracoVault,thenerdery/UmbracoVault,wkallhof/UmbracoVault.Lite