Revert "[lldb] Move PassthroughScriptedProcess to `lldb.scripted_process` module"

This reverts commit 273a2d33, since it
might be the cause for `TestStackCoreScriptedProcess` and
`TestInteractiveScriptedProcess` failures on GreenDragon:

https://green.lab.llvm.org/green/job/lldb-cmake/55460/`