use build.sourceversion in cache image key (#15019)
### Description
Use build.sourceversion in docker image cache key.
### Motivation and Context
We used filpath as the cache key in #14496.
In most cases, the docker base image tag is latest.
So, the hash of the files couldn't be aware of the change of base image.
As the result, the docker image restored, but the image will still be
rebuilt .
The maintenance cost would be huge if we pin image hash in docker file.
For example,
https://quay.io/repository/pypa/manylinux2014_x86_64?tab=tags&tag=latest,
it's updated almost every week.
So far, the build.sourceversion is the right way to keep cache is
updated and valid.
