PR: Add ipython_pygments_lexers as a new dependency

[takluyver]

Description of Changes

The IPython Pygments lexers are moving to a separate package (ipython/ipython#14520). Importing the IPython classes from IPython.lib.lexers will still work for a while, but importing the incidental things which that module imported from pygments won't, so I've switched those imports to point to pygments.

Issue(s) Resolved

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[takluyver]

I see the tests still run on some older versions of Python. I started ipython_pygments_lexer testing with Python >=3.11, the same as the development version of IPython, but I'm pretty sure it's not using any fancy features, so it's probably easy to support older Python versions. What's the minimum that we want?

[takluyver]

I've extended compatibility back to Python 3.8, as that didn't need any code changes.

[ccordoba12]

Thanks @takluyver for your help with this! You also need to add the new dependency to

• binder/environment.yml
• requirements/main.yml
• spyder/dependencies.py

We have a test that checks that dependencies in those files, plus setup.py, are in sync. In addition, the package needs to be available in Conda-forge too for this work.