Fix CUDA adapter to properly map P2P access errors:
- Map CUDA_ERROR_PEER_ACCESS_ALREADY_ENABLED to UR_RESULT_ERROR_INVALID_OPERATION
- Map CUDA_ERROR_PEER_ACCESS_NOT_ENABLED to UR_RESULT_ERROR_INVALID_OPERATION
Initialize P2P access in urEnqueueKernelLaunchIncrementMultiDeviceTest:
- Add urUsmP2PEnablePeerAccessExp calls in SetUp() for cross-device memcpy
- Add urUsmP2PDisablePeerAccessExp calls in TearDown() for cleanup
- Skip P2P operations for duplicate device handles (single GPU case)
- Accept INVALID_OPERATION for already-enabled or unsupported pairs
This fixes test failures on multi-GPU CUDA systems where P2P must be
explicitly enabled before cross-device USM memory operations.
Fixes #19033 

Changes:
- Track enabled P2P pairs in member variable enabledP2PPairs
- SetUp: Only record pairs WE successfully enabled (both SUCCESS)
- TearDown: Disable P2P bidirectionally for our pairs, ignore errors
- Removes global P2P state dependency between test instances
Works for both:
- 2 physical GPUs duplicated ×ばつ (8 logical devices)
- 8 distinct physical GPUs
Fixes #19033