Prepare for Python 3.13

[naufraghi]

• drop Python 2.7, 3.6 and 3.7 (support Python 3.8+)
• upgrade from windows-2019 to 2020
• upgrade from ubuntu-20.04 to 22.04
• upgrade from macos-11 to 13 and 14
• update actions to the latest version
• remove x86_64 and arm64 and keep only universal2 for macos (follow-up from https://github.com/naufraghi/tinyaes-py/pull/45#discussion_r1715630558)

See #45

[adehad]

just checking in, if anything is blocking this?

[naufraghi]

Not really, just other duties. I'll try to launch a pre today and later a final

[naufraghi]

Done in #51, thanks @adehad for the contributions!