Suite shard destination is now resolved from the requested test plan

The suite shard destination resolver now threads the requested test plan through platform inference and concrete simulator lookup. For schemes with multiple test plans, sharding resolves the simulator (for example platform=iOS Simulator,id=<UDID>) from the same target/platform family as the build, instead of falling back to a generic platform=iOS Simulator destination that Xcode rejects with exit code 70 during test enumeration.