tools: rename GDB plugin to pynuttx/nxgdb and enable PyPI packaging

[XuNeo]

Summary

Renames tools/gdb/nuttxgdb → tools/pynuttx/nxgdb

Establishes pynuttx as the root directory for future Python package development

Prepares for publishing nxgdb as an installable package (pip install nxgdb)

Impact

Enables direct package import in GDB:

(gdb) py import nxgdb  # Instead of manual path sourcing

Simplifies dependency management via PyPI

The original method still works, allowing to import latest python script, making it easy during python script development.

(gdb) source /path/to/nuttx/tools/pynuttx/gdbinit.py

Future Work

Gradually migrate other Python utilities to pynuttx and publish pynuttx as a namespace package.

Testing

Test package already published on PyPI (nxgdb)

Verified working installation flow:

qemu + GDB, now we can use py import nxgdb and legacy source gdbinit.py

[nuttxpr]

[Experimental Bot, please feedback here]

Yes, this PR appears to meet the NuttX requirements. It provides a clear summary of the changes, their rationale, and their impact. The impact section addresses all relevant points, highlighting the benefits for users (easier import and dependency management) and acknowledging future development plans. Testing confirms functionality through both PyPI installation and the existing manual method. The provided links to the PyPI package and clear testing descriptions further strengthen the PR.