Deprecate Evented and @ember/object/events (RFC 1111)

[NullVoxPopuli-ai-agent]

Implements RFC 1111: Deprecating Ember.Evented and @ember/object/events.

This finishes the work started in #20970 (the squashed original work is preserved with @wagenet as author; a follow-up commit rebases it onto current main and resolves the open questions).

What this deprecates

All under the single id deprecate-evented (since: { available: '7.3.0' }, until: '8.0.0', staged as available only since the RFC is at the Accepted stage):

• Applying the Evented mixin (via a new internal mixin-deprecation mechanism: setDeprecation/findDeprecation fire in Mixin#reopen when a deprecated mixin — or a mixin containing one — is applied, DEBUG-only)
• Calling the Evented methods on/one/off/trigger/has (including on framework classes like classic Component, Route, and EmberRouter)
• addListener/removeListener/sendEvent imported from @ember/object/events (deprecating wrappers; the internal @ember/-internals/metal implementations remain silent)
• The on() event decorator from @ember/object/evented

RouterService exemption

Per the RFC, RouterService's event methods are not deprecated: it no longer extends Evented and instead implements on/one/off/trigger/has directly on top of the internal (non-deprecating) listener functions, with routeWillChange/routeDidChange documented types.

Framework internals fire no deprecations

• Internal mixin applications (CoreView, Route, EmberRouter) are wrapped in disableDeprecations()
• Classic component lifecycle events (didInsertElement, willRender, …) and EventDispatcher dispatch now go through new internal sendCoreViewEvent/hasCoreViewListener helpers instead of view.trigger()/view.has()
• Route activate/deactivate and EmberRouter routeWillChange/routeDidChange use internal sendEvent directly
• Mixin observer/listener bookkeeping uses the internal addListener/removeListener

This is proven by the ALL_DEPRECATIONS_ENABLED=true suite run: any unexpected deprecation fails a test, and all 9427 tests pass.

Differences from #20970

• Deprecation id settled as deprecate-evented (was placeholder ember-evented), versions updated from 6.12.0 to 7.3.0; the guide in Add deprecation guide for Ember.Evented and @ember/object/events ember-learn/deprecation-app#1404 (evented.md) should be renamed to deprecate-evented.md and its versions updated to match
• Rebased onto current main: deep-path imports (ember-local/no-barrel-imports), the removed packages/ember barrel, and the reorganized glimmer internals
• The previously failing smoke tests and Node.js tests pass (failures appear to have been staleness of the old branch)

Verified locally

• Browser suite in all four variants: default, ALL_DEPRECATIONS_ENABLED=true, OVERRIDE_DEPRECATION_VERSION=15.0.0, production — 0 failures
• All 7 smoke-test scenarios (classic, embroider webpack/vite, strict resolver, node), plus classic-basics with OVERRIDE_DEPRECATION_VERSION=15.0.0
• type-check:internals, type-check:types, eslint, prettier, node tests, docs coverage

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