Feat(move-on-aptos): v2 features

[ArArgon]

• Move on aptos v2 features:
  • Enum
  • Match pattern
  • Positional fields
  • Package visibility
  • Alternative syntax for struct and enum
• Bug fixes
  • vector[...] is correctly parsed
  • Change return's precedence
  • Some grammar clean-ups

Security

• [x] Change has no security implications (otherwise, ping the security team)

[nmote]

I've updated https://github.com/semgrep/semgrep-move-on-aptos with these changes.