Rewrite RealMapBinder to use InternalFactory

This CL is a performance refactor.

This does change the SPI dependency tree, in a way I believe more accurately
describes the dependencies of each of the maps provided. Previously the dependencies for all maps was just a dependency on the entrySetBinder, which contained providers for all of the values. The new implementation has dependencies directly on the Vs for Map<K, V> and the multimap versions (e.g. Map<K, Set<V>>), and dependencies on Provider<V> for Map<K, Provider<V>> and the mutimap versions (e.g. Map<K, Set<Provider<V>>>).

This implementation follows the same pattern as OptionalBinder, notably
* All the mutable state is moved into a new inner class named BindingSelection
* Calculating keys + set names is delayed until configure()/initialization time
* None of the factories need circular deps resolution

Caliper benchmarks show an improvement in all four bindings provided by
MapBinder:
https://caliper.[].com/runs/280cbcdd-9853-46a6-9852-2d591fc8b848,bfa5c0d0-002a-4eaa-9984-d4ac459daf16#r:scenario.benchmarkSpec.methodName,run.label
(command used: [] run --run_under=perflab -- experimental/users/lukes/benchmarks:InjectionBenchmark -b timeMultimapBinderMultimapBinding,timeMultimapBinderMultimapProviderBinding,timeMultimapBinderMapBinding,timeMultimapBinderMapProviderBinding -t 3 -r {head, with_change})

This has been run on the tap train and no failures are believed to be
associated with this CL:
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