Go scripts: update for 1.20, Mach-O support, UTF-8 static strings, amd64 dynamic string detection update, tweaks

[monoidic]

This PR:

• adds support for Go 1.19 and 1.20 (the latter of which has a new pclntab magic)
• added register-based dynamic string detection
• adds support for UTF-8 static strings
• includes various reworking of existing code

[monoidic]

Note (partially to self): my new and improved™ version detection does not appear to work properly on some older binaries, due to the version string not being given in the specified section. Gonna try looking at solutions (e.g testing multiple sections and/or falling back to the original behaviour).