Nexpy

* Fixes a bug in the Scan Panel when a scan variable is missing in some files.
* Adds support for PyQt6 and PySide6.

* Fixes a bug when masking data in the Fit Panel.
* Fixes compatibility with the upcoming Matplotlib v3.6 release while preserving backward compatibility to v3.4.
* Removes the `Magic` menu, which is no longer included in the Jupyter QtConsole and contains deprecated functions. The IPython `magic` commands will still work in the shell.
* Updates the dependence on `ipykernel` to remove versions that contained a bug in the in-process kernel.

* Adds an option to plot projections with weights.
* Adds support for setting expiry times for stale locks.
* Sets the default entry to the currently selected entry in`Choose Entry` dialogs.
* Fixes the default file name when exporting plot windows.

* Fixes compatibility with older versions of Matplotlib.
* Fixes a bug when removing all files from the tree.
* Improves widgets used by plugin menus.

* Removes attempt to set the PyPlot backend in the default startup script to reduce potential problems in some systems. This allows a new user to customize their preferred backend by customizing the script after the initial launch.

* Uses HDF5 virtual datasets to consolidate data from multiple files in the Scan Panel.
* Adds virtual dataset metadata, such as file sources, to the View Dialog.
* Adds support for qualitative color maps (`tab10` and `tab20`) with automatic alignment of integer values to the discrete color bands.
* Enhances the options available for labeling 1D plot legends.
* Drops support for PyQt4, now that it is no longer supported by Matplotlib. PyQt5 and PySide2 are currently supported.
* Converts package to use the latest recommendations for package distribution, such as creating a pyproject.toml file to configure the build backend, moving metadata and requirements from setup.py to setup.cfg, and using setuptools_scm for version management.
* Improves PEP-8 compliance of code.