Add native vsock support to ADB.

vsock is a socket address family for communicating into and out of
virtual machines. Addresses have a port and CID. The CID is unique to
each virtual machine on the computer. The VM host always has CID 2.
http://man7.org/linux/man-pages/man7/vsock.7.html

Inside the android guest, the adb daemon hosts a vsock server with
VMADDR_CID_ANY, automatically using the guest CID. The adb server
can now connect to addresses of the form vsock:cid:port, where the CID
must be specified and the port defaults to 5555.

This is a significant speed improvement for ADB connections in
Cuttlefish, with 150-200 MB/s for `adb push` and 100-150 MB/s for
`adb pull`. It also allows removing some proxying steps from Cuttlefish,
simplifying the full connection path, and removes a dependency on the
unstable ivshmem protocol.

Commands tested against a Cuttlefish VM with CID 3:
adb connect vsock:3:5555
adb -s vsock:3:5555 shell
adb disconnect vsock:3:5555

Supporting "adb disconnect" and "adb -s" required modifying some of the
parts that parse addresses / serials.

push/pull trials with native adb vsock support in cuttlefish:

100m: 1 file pushed. 297.6 MB/s (104857600 bytes in 0.336s)
100m: 1 file pushed. 270.3 MB/s (104857600 bytes in 0.370s)
100m: 1 file pushed. 271.7 MB/s (104857600 bytes in 0.368s)
100m: 1 file pushed. 250.5 MB/s (104857600 bytes in 0.399s)
100m: 1 file pushed. 277.1 MB/s (104857600 bytes in 0.361s)
100m: 1 file pushed. 263.5 MB/s (104857600 bytes in 0.379s)
100m: 1 file pushed. 242.6 MB/s (104857600 bytes in 0.412s)
100m: 1 file pushed. 271.8 MB/s (104857600 bytes in 0.368s)
100m: 1 file pushed. 267.1 MB/s (104857600 bytes in 0.374s)

/data/local/tmp/100m: 1 file pulled. 212.8 MB/s (104857600 bytes in 0.470s)
/data/local/tmp/100m: 1 file pulled. 236.7 MB/s (104857600 bytes in 0.423s)
/data/local/tmp/100m: 1 file pulled. 201.2 MB/s (104857600 bytes in 0.497s)
/data/local/tmp/100m: 1 file pulled. 255.6 MB/s (104857600 bytes in 0.391s)
/data/local/tmp/100m: 1 file pulled. 199.6 MB/s (104857600 bytes in 0.501s)
/data/local/tmp/100m: 1 file pulled. 214.6 MB/s (104857600 bytes in 0.466s)
/data/local/tmp/100m: 1 file pulled. 254.2 MB/s (104857600 bytes in 0.393s)
/data/local/tmp/100m: 1 file pulled. 212.5 MB/s (104857600 bytes in 0.471s)
/data/local/tmp/100m: 1 file pulled. 218.9 MB/s (104857600 bytes in 0.457s)
/data/local/tmp/100m: 1 file pulled. 223.6 MB/s (104857600 bytes in 0.447s)

Bug: 121166534
Change-Id: I50f21fb5c9acafb8daa789df4e28c9e1bbbbf2ef
Test: adb connect/shell/disconnect
diff --git a/adb/adb.cpp b/adb/adb.cpp
index 06e4c50..a5b2f7b 100644
--- a/adb/adb.cpp
+++ b/adb/adb.cpp
@@ -1134,7 +1134,9 @@
         std::string host;
         int port = DEFAULT_ADB_LOCAL_TRANSPORT_PORT;
         std::string error;
-        if (!android::base::ParseNetAddress(address, &host, &port, &serial, &error)) {
+        if (address.starts_with("vsock:")) {
+            serial = address;
+        } else if (!android::base::ParseNetAddress(address, &host, &port, &serial, &error)) {
             SendFail(reply_fd, android::base::StringPrintf("couldn't parse '%s': %s",
                                                            address.c_str(), error.c_str()));
             return true;