narrow _load_plugin exception handler in plugins.finder

[HrachShah]

_load_plugin in src/flake8/plugins/finder.py catches bare 'except Exception as e' around plugin.entry_point.load() and rewraps the error as a FailedToLoadPlugin. The narrow set of failures that importlib.metadata.EntryPoint.load() can actually raise is:

• AttributeError: the entry-point's group is missing from the metadata, or the .value attribute is malformed
• ImportError: the module named in the entry-point spec does not import cleanly (SyntaxError in the user's plugin, missing init.py, or a circular import)
• ModuleNotFoundError: the package is not installed in the active environment, the entry point points to a module that has been removed, or a relative import failed
• ValueError: the entry-point spec string is malformed (not of the form 'package.module:attr'), the attrs don't exist in the package, or the resolver rejected the spec

Other Exception subclasses (e.g. OSError, TypeError, RuntimeError, KeyError, IndexError) are not on this path: OSError would indicate a flake8 host bug (e.g. permissions on the wheel cache), and TypeError/KeyError/IndexError are programming bugs in importlib that already raise from the resolver as one of the four above. Listing the specific exception types makes the catch self-documenting and lets KeyboardInterrupt/SystemExit propagate to the asyncio/multiprocessing pool machinery that owns the future, rather than being silently converted into a 'failed to load plugin' report that hides the user's Ctrl-C.

[asottile]

an import can raise an arbitrary exception so first no.

also this llm is bad and assumes KeyboardInterrupt and SystemExit subclasss Exception 😆

please actually do your own work next time instead of throwing slop over the fence