MNT remove obsolete Python 2 syntax, add some types

[kroq-gar78]

This will make it easier to use newer Python features (e.g. type annotations).

[Copilot]

Pull request overview

This PR modernizes the codebase by removing legacy Python 2/early-Python-3 compatibility patterns, making it easier to adopt newer Python features (e.g., clearer type annotations and super() usage).

Changes:

• Replace Python 2-era class declarations (class X(object)) with Python 3 syntax (class X), and modernize super(...) calls to super().
• Convert dict((k, v) for ...) patterns to dict comprehensions and update string formatting to f-strings.
• Remove builtins/__future__ compatibility imports and a Python 2-only setdefaultencoding block.

Reviewed changes

Copilot reviewed 21 out of 21 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
cortex/xfm.py	Update class declaration to Python 3 style.
cortex/utils.py	Convert dict construction to comprehension (but leaves one Python 3-incompatible expression nearby).
cortex/svgoverlay.py	Remove builtins compatibility import and modernize class declarations.
cortex/segment.py	Remove Python 2 builtins.input compatibility import.
cortex/rois.py	Update class declaration and dict-building syntax.
cortex/quickflat/utils.py	Use f-strings and dict comprehensions for cleaner modern Python.
cortex/quickflat/composite.py	Use f-strings for exceptions/logging.
cortex/mayavi_aligner.py	Use super() and dict comprehensions; modernize legacy patterns.
cortex/mapper/mapper.py	Update class declaration to Python 3 style.
cortex/mapper/init.py	Use f-string for cache filename construction.
cortex/freesurfer.py	Remove __future__/builtins Python 2 compatibility imports; modernize class declaration.
cortex/dataset/views.py	Update class declarations, dict comprehension usage, and modern super() calls; refine typing.
cortex/dataset/viewRGB.py	Modernize super() calls.
cortex/dataset/view2D.py	Modernize super() calls.
cortex/dataset/dataset.py	Update class declaration to Python 3 style.
cortex/dataset/braindata.py	Modernize super() usage and simplify Python 2 string-type compatibility logic for xfmname.
cortex/database.py	Remove Python 2 builtins.input compatibility import; update class declarations and dict-building syntax.
cortex/brainctm.py	Update class declarations and modernize super() usage.
cortex/appdirs.py	Update class declaration to Python 3 style.
cortex/align.py	Remove Python 2 builtins.input compatibility import.
cortex/init.py	Update deprecated helper class syntax and remove Python 2-only encoding workaround.

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[kroq-gar78]

Superseded by #666 .