Instead of using a fallback strategy to locate a configuration-cache entry
based on the current job and git SHA, these entries are now keyed based on their
file content with the keys persisted in the primary Gradle User Home entry.
This removes the chance of having a configuration-cache entry restored that is
incompatible with the restored Gradle User Home state, and makes the logic easier
to understand.
This change involved a fairly major refactor, with the CacheEntryExtractor being
split out from the primary cache implementation, and adding a separate extractor
implementation for configuration-cache.
Previously, the action was restoring/saving the configuration-cache data for each
step that applied the action. In order to support Gradle invocations that are _not_
managed by the action, the configuration-cache restore is now performed in the initial
action step, and save is performed in the final post-action step.
The build root directories are recorded for each invocation via an init script.
Instead of relying on the separate cache implementations to check for the
existence of cached products, we now explicitly track whether or not the execution
is the first time the action has been invoked for a job.
Instead of tracking a single 'fully-restored' flag, track the restore status of each
cache entry restore. If any of these are requested but not restored, then the overall
Gradle User Home cache is not fully restored.
Added special handling for the case when zero artifact bundles are set: this is used
in tests to simulate a not-fully-restored state.
