vmm: vstate unit tests cleanup
vmm: vstate unit tests cleanup

Simplified and cleaned-up the following unit tests:
- renamed test_create_vm to test_get_supported_cpuid as the
  function being tested is actually get_supported_cpuid. Also,
  moved the configure for x86_64 before the definition of test
  instead of placing it before calling get_supported_cpuid.
- squashed test_vm_memory_init_success and test_vm_memory_init_fail
  in one test called test_vm_memory_init. Also, deleted the calls
  to get_memory on which we called read and write as these
  operations are not related to the memory_init(), but to the
  implementation of the GuestMemory. That functionality is already
  tested in the memory_model crate.
- removed test_setup_irqchip_failure and move the error case in
  the the x86_64 specific test_setup_irqchip.
- renamed invalid_seccomp_lvl to test_vcpu_run_failed.
- delete not_enough_mem_slots as it was testing the error cases
  already tested in test_vm_memory_init.

Signed-off-by: Andreea Florescu <f68a7d732e796861f8e79ea704b43a5ee52eddaf@amazon.com>

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