* cli: added --safety=full|none flag to maintenance commands
This allows selection between safe, high-latency maintenance parameters
which allow concurrent access (`full`) or low-latency which may be
unsafe in certain situations when concurrent Kopia processes are
running.
This is a breaking change for advanced CLI commands, where it removes
timing parameters and replaces them with single `--safety` option.
* 'blob gc'
* 'content rewrite'
* 'snapshot gc'
* pr renames
* maintenance: fixed computation of safe time for --safety=none
* maintenance: improved logging for blob gc
* maintenance: do not rewrite truly short, densely packed packs
* mechanical: pass eventual consistency settle time via CompactOptions
* maintenance: add option to disable eventual consistency time buffers with --safety=none
* maintenance: trigger flush at the end of snapshot gc
* maintenance: reload indexes after compaction that drops deleted entries, this allows single-pass maintenance with --safety=none to delete all unused blobs
* testing: allow debugging of integration tests inside VSCode
* testing: added end-to-end maintenance test that verifies that full maintenance with --safety=none removes all data
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