LogBoxData test migrated to Jest modern timers

[chicio]

Summary:

This PR migrates the LogBoxData tests so that it uses Jest modern timers.
I removed the legacyFakeTimers property from useFakeTimers (like I did in the previous PR for Pressability tests #55410), and moved it to a beforeEach. This in combination with restoring real timers in afterEach improves tests reliability and isolation.
Then I modified some tests that started to fail by adding explicit flushToObservers().
The extra flushToObservers() calls are necessary because addLog/addException schedule processing using setImmediate, and inside that callback handleUpdate() schedules observer notifications using another setImmediate (so we need to flush twice to simulate the correct behaviour like it was already done in some other tests in the test suite).

Changelog:

[GENERAL] [CHANGED] - Migrated LogBoxData tests to Jest modern timers

Test Plan:

• Ran LogBoxData-test and verify all tests cases passed
• Ran the React Native test suite to ensure all tests pass
• Verified test correctness by intentionally breaking production code after fixing the tests (eg. removing the handleUpdate call in addException, that changes the call to the observer)