[expo-updates] Break up E2E tests for better reliability (#21223)

# Why

Attempting to run both basic and assets tests in the same on-success EAS
hook is having problems, and occasionally leading

[expo-updates] Break up E2E tests for better reliability (#21223)

# Why

Attempting to run both basic and assets tests in the same on-success EAS
hook is having problems, and occasionally leading to infinite loops
until the container is forcibly stopped.

# How

Break up the E2E tests into four workflows, that will each run in a
shorter time and more reliably.

We also now only run the assets tests on changes to the expo-updates module itself, to reduce the CI load.

# Test Plan

E2E tests should pass reliably.

# Checklist

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

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