Parallelize compress/upload of cerbero deps
Currently the cerbero CI looks like this:
- build cerbero deps
- compress (xz) cerbero deps cache
- upload cerbero deps cache
- decompress (xz) + extract cerbero deps cache
- build cerbero package
- upload cerbero package
We can change this to:
- build cerbero deps
- create cerbero deps cache using tar (uncompressed)
- extract cerbero deps cache using tar
- build cerbero package + (in parallel) compress cerbero deps cache using xz and upload it
- upload cerbero package
This should save some time, especially on the mac runners which have fewer cores for xz to use.