Migrate from ConcurrentDictionary to Dynamic Static Generic Caches

[LordZoltan]

Having identified ConcurrentDictionary as being one of (but not the only) bottleneck, despite its very good performance, I've come up with a new solution which is valid for long-lived objects, such as containers (and, potentially, root target containers).

It requires adding specific TFMs to Rezolver for the runtimes which support System.Reflect.Emit APIs such as AssemblyBuilder, TypeBuilder etc - and leverages the static field initialisers to initialise objects statically which would either:

• need to be created each time a call is made, but which vary only by a type (which can, therefore, be used as generic arguments
• use the standard ConcurrentDictionary pattern of a thread-safe GetOrAdd()

Using static initialisers of dynamic types automatically provides thread-safe initialisation but without any performance penalty for accessing the protected data on subsequent reads. Just applying this pattern to both ResolveContext and the ICompiledTarget for strong-typed Resolve operations has provided a big reduction in memory overhead and performance.