Get rid of unused EntityFieldValueGet event

[SergeiPavlov]

Note

Medium Risk
Removes a public session event, which is a breaking change for external subscribers even if unused internally.

Overview
Removes the EntityFieldValueGet session event and all code that raised it when entity field values were read.

SessionEventAccessor no longer exposes the event or NotifyFieldValueGet. Entity.SystemGetValue no longer notifies system or session events on get; entity-level get subscriptions are unchanged. SessionEventsTest drops EntityFieldValueGet wiring and assertions that expected the event after reading a property.

This is a breaking public API change for any code that subscribed to EntityFieldValueGet; field set events are unaffected.

^{Reviewed by Cursor Bugbot for commit cb8d7d0. Bugbot is set up for automated code reviews on this repo. Configure here.}

[cursor]

Cursor Bugbot has reviewed your changes using default effort and found 1 potential issue.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, have a team admin enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 8a24371. Configure here.}