Rename trait to allowed_kernelspecs

[blink1073]

Partially addresses #642 by deprecating KernelSpecManager.whitelist in favor of the more descriptive and inclusive KernelSpecManager.allowed_kernelspecs.

[kevin-bates]

The changes look good Steve, thank you for providing this. I just had a couple of comments. I've run with this branch and see the appropriate deprecation warning:

[W 14:52:14.292 NotebookApp] KernelSpecManager.whitelist is deprecated in JupyterLab 7.0, use KernelSpecManager.allowed_kernel_names instead

My first thought on the trait name was allowed_kernels but I think allowed_kernel_names is more correct. I suppose another option would be allowed_kernelspecs so that kernel names aren't accidentally interpreted as "ipykernel" or "xeus-python", etc. i.e., the literal kernel name.

[kevin-bates]

Per a sidebar, I've suggested the trait name be allowed_kernelspecs to potentially avoid ambiguity.

The title could probably use an update as well, but didn't want to assume the suggestions would be accepted. 😄

[blink1073]

Thanks! I updated the title and description accordingly.

[vidartf]

[W 14:52:14.292 NotebookApp] KernelSpecManager.whitelist is deprecated in JupyterLab 7.0, use KernelSpecManager.allowed_kernel_names instead

Did we release Jupyterlab 7 already??? 😮 🎉

[blink1073]

Did we release Jupyterlab 7 already??? 😮 🎉

Haha fixes are welcome. 😉

[vidartf]

#674