* testing: KOPIA_TEST_LOG_OUTPUT logs subcommand outputs
* cli: additional flags for 'blob list'
* Makefile: run all tests against epoch-based index manager
* epoch: added support for deletion watermark, which keeps track of latest maintenance which dropped index entries
* content: added deletion watermark to content manager
* maintenance: improved maintenance without safety to force rewrites
* maintenance: skip quick maintenance when epoch manager is enabled
* maintenance: do not enable quick maintenance when epoch manager is used
* testing: skip TestIndexOptimize when running against epoch manager-backed index strutures