Collect crash dumps using diagnostics netclient

[nohwnd]

Description

• Set environment variables as described here https://github.com/dotnet/runtime/blob/fab4f6e674404f1d88753529f7461d1bed24cb2e/docs/design/coreclr/botr/xplat-minidump-generation.md to collect dumps on crash, from test host and child processes. Little complication is that we need to set them up in the process that starts testhost (vstest.console) but collect the logs in datacollector, and we need to set them up bevore starting test host, so vstest.console will need to know what to do. 🙁

• Collect the dump and all child dumps created this way

• add timestamp and name to the dump

Related #2380