Create RemoteImage RemoteInstance classes.

- Add kernel_build_id in avd_spec for cuttlefish remote instance.
- handling AVD config the legacy way (cfg) and the new way (AVDSpec)
- adding new metadata to the gce instance to enable other acloud features

Bug: 114166856
Test: m acloud && acloud create
atest acloud_test
Change-Id: Id9ec431e84a6311db9ba09d1fa3ee102452d4957
diff --git a/internal/constants.py b/internal/constants.py
index 9586caa..e64c6ba 100755
--- a/internal/constants.py
+++ b/internal/constants.py
@@ -28,6 +28,11 @@
 DEFAULT_SERIAL_PORT = 1
 LOGCAT_SERIAL_PORT = 2
 
+# Remote image parameters
+BUILD_TARGET = "build_target"
+BUILD_BRANCH = "build_branch"
+BUILD_ID = "build_id"
+
 # AVD types
 TYPE_GCE = "gce"
 TYPE_CF = "cuttlefish"
@@ -77,5 +82,7 @@
 )
 HW_PROPERTIES = [HW_ALIAS_CPUS, HW_ALIAS_RESOLUTION, HW_ALIAS_DPI,
                  HW_ALIAS_MEMORY, HW_ALIAS_DISK]
+HW_X_RES = "x_res"
+HW_Y_RES = "y_res"
 
 USER_ANSWER_YES = {"y", "yes", "Y"}