Flakey Test: handles schema import during content request

[DanRod1999]

It looks like handles schema import during content request has been timing out rush cover in windows and linux. Build does not show logs clearly that test is failing, but appears to stop right after the previous test, so I believe it is hanging during this test. So far I've only seen it on windows and linux.
Example

Introduced in PR

[grigasp]

#8745 (comment)

[grigasp]

I managed to reproduce locally, and it looks like the deadlock is in ECDb code:

• Thread 46420 holds ECDb's mutex in MainSchemaManager::ImportSchemas and is waiting for workers to complete.
• Thread 44876 is one of the workers that Thread 46420 is waiting for and is hung trying to acquire ecdb.GetImpl().GetMutex().

Repro steps on Windows:

1. Checkout master branch of itwinjs-core
2. Add .only on this test
3. rush install
4. rush build -t presentation-full-stack-tests
5. cd full-stack-tests\presentation
6. .\run-forever.bat

It's helpful to execute the run-forever.bat in multiple terminal windows at the same time (I ran it in parallel in 4 terminals). For me it takes ~20-30 runs until one of the terminals hangs.

@khanaffan, can you have a look? I also have a dump locally if you can't reproduce it - ping me if you need it.