Provide a less disruptive client reset experience with a new “seamless loss” mode that will reset the clients to the state of the server, but will lose local client changes.

• [x] API design
• [x]Add parsing of sync configuration (C++)
• [x] Add functor classes for the two new call backs (C++)
• [x] API doc
• [x] TS defs
• [x] Rebase on master
• [x] Update to latest core commit
• Tests
  • [x] Simulate client reset (discard local)
  • [x] Simulate failure on client reset
  • [x] Update usage of _simulateError()

PR: https://github.com/realm/realm-js/pull/4082