Modern universal build for Apple Silicon

[zwaldowski]

Provides Apple Silicon-native builds of dependent frameworks and the app itself.

Completes #693. Includes #713.

• Builds libsqlite3 3.22.0, libcrypto 1.1.1h (previously 1.1.0g; that version did not support Apple Silicon with ASM optimization), libssh 1.9.0 (previously 1.8.0; that version did not support the newer OpenSSL) for Apple Silicon.
• Updates Sparkle to a recent version supporting Apple Silicon.
• Updates build scripts to produce xcframeworks. The app’s Xcode project no longer needs to pick out a framework for itself and, in the future, will fail with more clarity on missing architecture/platform combinations.
• Removes unused build of libmbedtls.

I recommend looking at the commits here individually: 9dfec8b isn’t meaningfully reviewable.

I agree to the contributor agreement, etc etc.

[lucasderraugh]

Wow, fantastic! I'll get to reviewing all your changes today if possible.

[lucasderraugh]

I'm going to address your other changes then return to this one so I can do a large rebase.

[lucasderraugh]

Everything looks good here. Nice touch with moving them to xcframeworks. Above and beyond what I had in my local branch 👍