* 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
* epoch: misc fixes and logging
* blob: misc helpers
* cli: removed useless 'repository upgrade', replaced by 'repository set-parameters'
* content: implemented indexBlobManagerV1 which uses epoch manager
* cli: commands to manipulate repository epoch parameters
* cli: commands to examine epoch-based indexes
* content: added test suite that uses epoch-based index manager
* content: fixed a ton of test data races caused by sharing blobtesting.DataMap
* cli: additional tests and validation for 'repository set-params'
* testing: replaced the use of suite with our own, since suite is not parallelizable
