* content: fixed repo upgrade version
Previously upgrade would enable epoch manager and index v2 but would
not set the version of the format itself. Everything worked fine
but it would not protect from old kopia opening the repository.
* ci: added compatibility test that uses real 0.8 and current binaries
* ci: refactored CI/CD logic & Makefile
- removed all travis CI emulation environment variables and replaced with:
CI_TAG=<empty>|tag
IS_PULL_REQUEST=false|true
- refactored all OS and architecture-specific decisions to use around standard GOOS/GOARCH values instead of uname/OS
- re-added self-hosted runner for ARMHF (3 replicas)
- added brand new self-hosted runner for ARM64 (3 replicas)
- disabled attempts to publish and sign on forks
- improved integration test log output to better see timings and sub-tests
- print longest tests (unit tests and integration) after each run
- verified that all configurations build successfully on a clone (jkowalski/kopia)
- run make setup in parallel
* testing: fixed tests on ARM and ARM64
- fixed ARM-specific alignment issue
- cleaned up test logging
- fixed huge params warning threshold because it was tripping on ARM.
- reduced test complexity to make them fit in 15 minutes
