Probe silos indirectly before submitting a vote (dotnet#6800) (dotnet…

…#6839)

* Probe silos indirectly before submitting a vote (dotnet#6800)

* Probe silos indirectly before submitting a vote

* Improve tests

* Remove no-longer necessary cases in SiloHealthMonitor, since concurrency has been removed.

* Changes for 3.4.0