Accumulate breaking changes

[ZenVoich]

• Remove mops install <pkg> in favor of mops add <pkg>
• Remove cache/config files migration code
• Drop support for Node.js <18
• Add support for pocket-ic v3
• Drop support for pocket-ic <3
• Remove notifyInstall on backend
• Remove MOPS_ENV?
• change default test reporter to files? verbose if only 1 test file?
• cli commands refactoring?
  • mops import-identity -> mops user import
  • mops whoami -> mops user get-principal
• remove // compatibility with older versions from mops.ts
• Use mops sources --no-install in vscode extension