Add Instance class for list and delete command.

Use Instance class to encapsulate instance properties and methods.
Instance object could be initialize by two way:
- process a gce instance which is queried from google compute api.
- parse the instance detail from launch_cvd process.

Bug: 118405737
Test: atest acloud_test
Change-Id: I44edbc63987347c11ed42631a3a4641cf4ff967d
5 files changed