Port 090-task-status.t etap test suite to eunit

Split huge test case into multiple ones. Fix issue with get_task_prop
when Acc may be reset if searched task isn't last in the list.
Port 100-ref-counter.t etap test suite to eunit
Port 120-stats-collect.t etap test suite to eunit
Port 121-stats-aggregates.t etap test suite to eunit

Merged into couch_stats_tests suite.
Port 130-attachments-md5.t etap test suite to eunit

Add random document id generator macros.
Have to use handmade http client instead of ibrowse since it makes too
complicated sending chunked requests.
Port 140-attachments-comp.t etap test suite to eunit

- Merge into couchdb_attachments_tests suite;
- Add PUT requests to test_request util;
- Remove dependency from files outside fixtures directory;
- Group test cases to reduce amount of duplicate code;
- Fix hidden issue with gzip encoding: for encoding_length stub info
  check using zlib:gzip on 2KiB+ files leads to mismatch by 2-4 bytes
  and this difference grows with file size. Using gzip fun code from
  couch_stream solves the issue.
Port 150-invalid-view-seq.t etap test suite to eunit

Merged into couchdb_views_tests suite.
Port 160-vhosts.t etap test suite to eunit

Split Rewrite and OAuth tests.
Port 170-os-daemons.t etap test suite to eunit
Port 171-os-daemons-config.t etap test suite to eunit

Merged into couchdb_os_daemons_tests suite.
Port 172-os-daemons-errors.t etap test suite to eunit

Merged into couchdb_os_daemons_tests suite.
Removed errors redirection to /dev/null to explicitly signal that
permissions are set correctly.
Port 180-http-proxy.t etap test suite to eunit
Port 190-json-stream-parse.t etap test suite to eunit
Port 200-view-group-no-db-leaks.t etap test suite to eunit

Merged into couchdb_views_tests suite. Apply minor refactor changes.
Port 201-view-group-shutdown.t etap test suite to eunit

Merged into couchdb_views_tests suite. Database population reduced
to speedup test and removed second view index call which leaded to
race condition when compaction becomes completed in time of view index
update call and before assertion check for {error, all_dbs_active}.
Port 210-os-proc-pool.t etap test suite to eunit
Port 220-compaction-daemon.t etap test suite to eunit
Port 230-pbkfd2.t etap test suite to eunit
Port 231-cors.t etap test suite to eunit

Extend vhost and subresource testing for more generic code.
Port 232-csp.t etap test suite to eunit