feat: perf enhancement for snyk monitor

[anthogez]

Rather than have post monitor working 1 by 1, we are trying to achieve an initial
and minimal concurrency of 5 monitor requests at once

[github-actions]

	Warnings
⚠️	Since the CLI is unifying on a standard and improved tooling, we're starting to migrate old-style imports and exports to ES6 ones. A file you've modified is using either module.exports or require(). If you can, please update them to ES6 import syntax and export syntax. Files found: src/cli/commands/monitor/index.ts
⚠️	You've modified files in src/ directory, but haven't updated anything in test folder. Is there something that could be tested?

Generated by 🚫 dangerJS against fecbcab

[PeterSchafer]

Suggestion: Let's be a bit more pessimistic to not increase the load too much and set it to a lower value first. Let's start with 2.