[router]: ensure navigation events are fired at correct target (#27485)

# Why

Expo Router was incorrectly firing events with the incorrect navigator
target. This would cause situations where the event was ignored or the
state in correct.

The result of this was a sublty incorrect routing state that was
- causing incorrect back history
- navigation state was at the incorrect level in the hierarchy.

# How

I rewrote `getNavigateAction` to get the action in a single pass.
Previously we were getting the action, and then refining the action
based up on the parent navigator.

This approach could have worked, but the structure of the navigation
action is, well, weird. This made converting an action into the targeted
action error prone.

The new approach is to first identify the target, and then build the
correct navigation action.

# Test Plan

The fixed heirarachy (and incorrect back behaviour) can be demonstrated
by [this
test](https://github.com/expo/expo/blob/0dd5fd0bea34c5d8faeb6b4ada8ea82cfe220c39/packages/expo-router/src/__tests__/push.test.ios.tsx#L12).
Now the routes are correctly pushing to the `<Stack />` inside the
`(group)`

This incorrect back behaviour can be demonstrated by [this
test](https://github.com/expo/expo/blob/0dd5fd0bea34c5d8faeb6b4ada8ea82cfe220c39/packages/expo-router/src/__tests__/stacks.test.ios.tsx#L98).
Notice how some routes were previously not added to the history, causing
the back behaviour to "skip" a route

# Checklist

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- [ ] Documentation is up to date to reflect these changes (eg:
https://docs.expo.dev and README.md).
- [ ] Conforms with the [Documentation Writing Style
Guide](https://github.com/expo/expo/blob/main/guides/Expo%20Documentation%20Writing%20Style%20Guide.md)
- [ ] This diff will work correctly for `npx expo prebuild` & EAS Build
(eg: updated a module plugin).

---------

Co-authored-by: Expo Bot <34669131+expo-bot@users.noreply.github.com>

packages/expo-router/CHANGELOG.md

@@ -11,6 +11,7 @@
 
 ### 🐛 Bug fixes
 
+- Ensure navigation events target the correct navigator ([#27485](https://github.com/expo/expo/pull/27485) by [@marklawlor](https://github.com/marklawlor))
 - Fix using array syntax `(a,b)` with server output. ([#27462](https://github.com/expo/expo/pull/27462) by [@EvanBacon](https://github.com/EvanBacon))
 - Fix issue with skipping all imports. ([#27238](https://github.com/expo/expo/pull/27238) by [@EvanBacon](https://github.com/EvanBacon))
 - Include search parameters in the default Screen.getId() function. ([#26710](https://github.com/expo/expo/pull/26710) by [@marklawlor](https://github.com/marklawlor))