Add module based host-tools snapshot

Add new module:
host_snapshot {
    name: "host-snapshot"
    deps: [
      (list of host tools)
    ],
    ...
}

Package host tools using android.PackagingBase to capture host tools and transitive packaging data.
Add JSON meta data to snapshot that allows snapshot to be installed via development/vendor_snapshot/update.py

Add support to generate a fake host snapshot of all host modules that is used to detect required
modules via development/vendor_snapshot/update.py.

Bug: 192556798
Bug: 194799048
Bug: 192896149
Test: m HOST_FAKE_SNAPSHOT_ENABLE=true host-fake-snapshot dist -- check snapshot exists in dist

Change-Id: I849c4db801cd858408f6fe6a3ce69262a23a5be9

android/config.go

@@ -1517,6 +1517,10 @@ func (c *deviceConfig) RecoverySnapshotDirsIncludedMap() map[string]bool {
 		c.config.productVariables.RecoverySnapshotDirsIncluded)
 }
 
+func (c *deviceConfig) HostFakeSnapshotEnabled() bool {
+	return c.config.productVariables.HostFakeSnapshotEnabled
+}
+
 func (c *deviceConfig) ShippingApiLevel() ApiLevel {
 	if c.config.productVariables.ShippingApiLevel == nil {
 		return NoneApiLevel