[debugger] Throw with short and easily caught message in debugger tests.

[ilonatommy]

Based on a few logs that had failures connected with internal virtual async Task<JObject> WaitFor(string what), e.g.:

• https://helixre107v0xdcypoyl9e7f.blob.core.windows.net/dotnet-runtime-refs-pull-107769-merge-ca3f5c019c784602bd/chrome-DebuggerTests.SetNextIpTests/1/console.f183cc1e.log?helixlogtype=result
• https://helixre107v0xdcypoyl9e7f.blob.core.windows.net/dotnet-runtime-refs-pull-107769-merge-ca3f5c019c784602bd/chrome-DebuggerTests.AsyncTests/1/console.636f3cf1.log?helixlogtype=result

The logs that look like this:
https://dotnet.github.io/core-eng/helix-workitem-deadletter.txt

If you’re reading this, that means the Helix work item you’re trying to find the logs for has dead-lettered.

What this means:

- All attempts to retry execution of this work item were unable to complete.  This can be both for infrastructure reasons (problems within Azure) or issues with the work item (for instance, causing a machine to reboot unexpectedly or killing the Helix client on the machine will force a retry).
- No further work will be done for this specific work item, and its exit code is set to an artificial -1 (since it did not complete, there is no real exit code).
...etc

might be created due to too long logs. Typically, WaitFor throws with logging a long json text. If we would catch that error and rephrase it, it will be easier for Known Issue to catch the logs. The debugger tests are due to be migrated soon, so loosing the details about the json that is logged should not be a problem.

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[ilonatommy]

Generally on this PR it works but we still have logs like:
https://helixre107v0xdcypoyl9e7f.blob.core.windows.net/dotnet-runtime-refs-pull-109011-merge-7b8a8a12269040d59f/chrome-DebuggerTests.GetPropertiesTests/1/console.dd12fe20.log?helixlogtype=result

Starting test execution, please wait...
A total of 1 test files matched the specified pattern.

...
[EXECUTION TIMED OUT]
Exit Code:-3Executor timed out after 3000 seconds and was killed

['chrome-DebuggerTests.GetPropertiesTests' END OF WORK ITEM LOG: Command timed out, and was killed]

Maybe it's also coming from WaitFor but does not manage to throw exception? Just to be sure, I will add a timeout in that method, let's say 10 sec per one WaitFor.