New Editors system roadmap

[saskliutas]

Roadmap for implementation and adoption of the new editors system:

• 5.4: Introduced the new property editor system. Components using the editors allow opting-in to using either the new or the legacy system, defaulting to the legacy one. https://github.com/iTwin/appui/releases/tag/release%2F5.4.0
• 5.5: Introduce an AppUI preview feature flag to enable the new editors system in tool settings. [preview-feature]: New editors system in tool settings #1289
• 5.x: Deprecated legacy editors system. Deprecate old editors system #1224
• 6.0: Switch the default editors system from "legacy" to "new", while still allowing to opt-out.
• 7.0: Remove the legacy editors system.

Miscellaneous (issues or tasks to reach feature parity):

• Add toolSettingsKeyPressCommit preview feature #1329
  • CustomNumberEditor used in the new editor system needs to be fixed (currently it tracks the entered value in the local state, which can get out of sync with actual property value)
  • Implement toolSettingsKeyPressCommit in new editor system