ability for sync verb handler to skip delete commit entries to be sent to client

[murali-shris]

Is your feature request related to a problem? Please describe.

https://github.com/atsign-foundation/at_server/issues/2066 "Excessive Syncing of Deleted Keys: New clients must sync all keys, including numerous deletions, leading to significant time and space inefficiencies."

Describe the solution you'd like

• introduce a flag skipDeletes in sync verb handler.
• do not send keys that were eventually deleted in the sync list to client

Describe alternatives you've considered

No response

Additional context

No response

[murali-shris]

Complete some of the changes on server to skip delete entries. While writing tests encountered a bug in _acceptKey in commit log keystore. https://github.com/atsign-foundation/at_server/pull/2115 Will fix the bug and then resume work on this feature

[murali-shris]

Server changes: https://github.com/atsign-foundation/at_server/issues/2097 Client changes: https://github.com/atsign-foundation/at_client_sdk/tree/sync_skip_deletes End2End testing in progress.Once successful, will run performance tests. Server PR to be merged first once performance results are good

[murali-shris]

Implemented skipUntil changes and extensive unit tests on server https://github.com/atsign-foundation/at_server/pull/2131 Changes in at_client in progress

[murali-shris]

https://github.com/atsign-foundation/at_client_sdk/pull/1432 At client changes complete.Will re-open PR once benchmarking tests are complete and server changes are merged Performance bench marking in progress https://docs.google.com/spreadsheets/d/1Mc4GFe2-xZ4CZImBa3xWiAufq7PaOm42c3pItTYSPXQ/edit?gid=0#gid=0