* 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
