Use GetType on a closed loaded assembly local

Replace FormatterServices.GetTypeFromAssembly on a closed Assembly.Load/LoadFrom/LoadFile local with assembly.GetType(name,false,false). Retain the loader, case sensitivity, missing-type result and name evaluation. Require a successful non-null BCL load and no other local references; borrowed/null/reassigned/escaping assemblies, lambdas, control-flow hazards and conditional files remain unchanged. Preserve caller trust and deserialization policy.