More startup work moved off the critical path

A second pass over what IPython does before it can show a prompt, on top of the lazy imports and lazy magic registration. Nothing here is visible in normal use; it is all work that used to happen on every start and is now either avoided or postponed until something actually needs it.

• Resolving a theme’s base pygments style no longer imports pygments.styles, and with it the pygments plugin machinery, importlib.metadata and email. Only the base style’s styles mapping was ever used, so for the builtin styles IPython’s own themes are based on the defining module is read directly. Styles that are not builtin – including any provided by a pygments plugin – still resolve exactly as before.

• Detecting whether the terminal speaks the kitty graphics protocol no longer imports psutil on Linux. The walk up the process tree needs each ancestor’s name and parent pid, and /proc/<pid>/stat has both. macOS still uses psutil. This one only ever showed up in an actual terminal: a headless ipython -c ... stops at the isatty check before reaching it. Setting IPYTHON_KITTY_GRAPHICS still skips detection entirely.

• The prompt style is built the first time it is drawn rather than each of the several times it is invalidated while a shell is being set up, and not at all for a run that never draws a prompt.

• More single-use imports moved to their use sites: platform, pprint, textwrap, html, mimetypes, locale, glob and runpy. The AST operator tables the terminal shortcut filters need moved out of IPython.core.guarded_eval into a module of their own, so evaluating a shortcut’s filter expression no longer imports the whole guarded evaluation machinery (and typing_extensions). They are still importable from IPython.core.guarded_eval.

Together this takes another ~13% off starting an interactive ipython in a real terminal, ~9% off ipython -c pass, and another ~43 modules off an interactive start, on top of the previous rounds.