[FEA]: Debugger pretty-printers: `cuda::std::complex`/`cuda::complex`

[Jacobfaib]

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

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

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

[HenrikGharagyozyan]

Hi! I'd like to work on this one. My plan is to follow the cuda::std::array printer pattern from #10528: add complex.py under libcudacxx/share/libcudacxx/gdb/ and libcudacxx/share/libcudacxx/lldb/, covering both cuda::std::complex and cuda::complex (both store __re_/__im_, so one matcher can handle the two class templates), plus exhaustive tests under libcudacxx/test/debugging/complex/ using the existing harness.

Note: I'll validate the gdb printer locally but don't have lldb available in my environment, so the lldb printer will mirror the gdb logic structurally and rely on CI for verification — flagging that upfront in case it needs extra review attention.