Remove `use_lldb_suite` from the package, and don't import it anymore.

This module was originally intended to be imported by top-level
scripts to be able to find the LLDB packages and third party
libraries.  Packages themselves shouldn't need to import it,
because by the time it gets into the package, the top-level
script should have already done this.  Indeed, it was just
adding the same values to sys.path multiple times, so this
patch is essentially no functional change.

To make sure it doesn't get re-introduced, we also delete the
`use_lldb_suite` module from `lldbsuite/test`, although the
original copy still remains in `lldb/test`

llvm-svn: 251963