fix critical vulnerabilities and remove unmaintaned dependency

[smolnikov]

This PR:

• ✅ removes the dependency on package koa-proxy which didn't have updates for 6 years now and introduces critical security vulnerabilities; replaces it with custom-made axios-based implementation of proxy
• ✅ updates other dependencies introducing vulnerabilities detected by npm audit
• ✅ resolves Outdated packages like @oclif/*, cli-ux, koa-proxy, and some more #33
• ❌ doesn't update the supported engine in package.json (to >=18 as many dependencies in package-lock.json already have it set, so current version doesn't truly support node 16) as this will require major version update

How it was tested:

• ✅ npm run build && npm run test

[smolnikov]

@anttiviljami could you share your opinion on this?