Improve P2P test.

- Ensure proper device is set before each command.

- Add command line switches:
    +bool p_memcpyWithPeer = false; // use the peer device for the P2P copy
    +bool p_mirrorPeers = false; // in addition to mapping current to peer
            space, map peer to current space.
    +int  p_peerDevice = -1;  // explicly specify which peer to use, else
use p_gpuDevice + 1.

tests/src/test_common.cpp

@@ -111,7 +111,7 @@ int parseStandardArguments(int argc, char *argv[], bool failOnUndefinedArg)
                failed("Bad iterations argument"); 
             }
 
-        } else if (!strcmp(arg, "--gpu") || (!strcmp(arg, "-g"))) {
+        } else if (!strcmp(arg, "--gpu") ||  (!strcmp(arg, "-gpuDevice")) || (!strcmp(arg, "-g"))) {
             if (++i >= argc || !HipTest::parseInt(argv[i], &p_gpuDevice)) {
                failed("Bad gpuDevice argument"); 
             }