Fix EFR32 Unit Test build

[rgoliver]

Problem

EFR32 Unit test fails to compile

Change overview

• Replace calls to usleep with the platform abstractions in chip::test_utils
• Remove the new TestCommands.cpp test which fails to compile on efr32:

/home/rgoliver/repo/connectedhomeip/src/test_driver/efr32/out/debug/../../third_party/connectedhomeip/zzz_generated/controller-clusters/zap-generated/IMClusterCommandHandler.cpp:5258: multiple definition of `chip::app::DispatchSingleClusterCommand(chip::app::ConcreteCommandPath const&, chip::TLV::TLVReader&, chip::app::CommandHandler*)'; obj/third_party/connectedhomeip/src/controller/tests/data_model/libInteractionTests.TestCommands.cpp.o:/home/rgoliver/repo/connectedhomeip/src/test_driver/efr32/out/debug/../../third_party/connectedhomeip/src/controller/tests/data_model/TestCommands.cpp:69: first defined here

Testing

Verified efr32 unit test builds, it still has a hardfault when running which can be addressed in another PR: #10447