[FEA]: Debugger pretty-printers: `cuda::std::tuple`

[Jacobfaib]

Create a lldb and gdb pretty printer for cuda::std::tuple.

The printer should live under libcudacxx/share/libcudacxx/<debugger>/tuple.py for each debugger.

In addition, the pretty printers should be exhaustively tested, with tests living under libcudacxx/test/debugging/tuple. See the existing tests in that directory for inspiration.

[dunga1k58bh]

@Jacobfaib Please check my PR, thank you.