[lldb] Fix some bugs in the Pipe class and add tests

- s/createUniqueFile/createUniquePath -- we don't want to create the file,
  just the file name
- s/data()/str().c_str()/ -- paths given to system apis must be
  null-terminated

GitOrigin-RevId: 13dea030b3d794d05a08dd0080c35844c9ca1b30
3 files changed