[AGP UTP] fix avdmanager cache

Allow Avd Manager cache to support multiple managers from different avd
folder. This is required for allowing ice box support with Gradle
Managed Devices, because we need to support caching of avd managers from
both the standard avd folder and the gradle managed avd folder.

Test: pre-existing. Added basic equality checks for the CacheKey
Bug: 141510559
Change-Id: I559ff54f3e35281149c1a5917678ae399615df05
7 files changed