Move lldb/test to lldb/packages/Python/lldbsuite/test.

This is the conclusion of an effort to get LLDB's Python code
structured into a bona-fide Python package.  This has a number
of benefits, but most notably the ability to more easily share
Python code between different but related pieces of LLDB's Python
infrastructure (for example, `scripts` can now share code with
`test`).

llvm-svn: 251532