Let's improve everything: less spaghetti code, scan algorithm and CI improvement, lighter binary

[pandatix]

Hi, St******* told me about this repo. I saw Go. I was not able not to contribute. 😄
So here is my PR (he challenged me to do it the 6th of april sooooo). I let you check what is new (pretty much everything) in the code, but here is a summary:

• 🍝 code spaghetti is now more readable (all the kernel is in internal at root)
• 📈 algorithm improvement (mainly on the scan load balancing, documented in code)
• 🚀 improve CI to make it advantageous for the devs (see the Actions for more info. Notice it removes darwin/386 build because is not compatible with Go 1.16)
• 🤖 add acceptance tests to enable functional tests and other implementations based on those
• 🙇 new TODOs/ideas submitted in README.md for open-source contributions

It also decreases the binary sizes with an average of -14,59%, according to the following.

Build	Old size	New size	Change
darwin/386	11596316	/	/
darwin/amd64	12963520	11244800	-15,28%
freebsd/386	11494919	9958457	-15,42%
freebsd/amd64	12959576	11398268	-13,70%
freebsd/arm	11464927	9954328	-15,18%
linux/386	11564173	10005288	-15,58%
linux/amd64	13023214	11423764	-14,00%
linux/arm	11525679	9900195	-16,42%
linux/mips	12573111	10889275	-15,46%
linux/mips64	13346334	11622775	-14,83%
linux/mips64le	13280928	11513243	-15,35%
linux/mipsle	12507649	10831225	-15,48%
linux/s390x	13162878	11341843	-16,06%
netbsd/386	11451592	9922778	-15,41%
netbsd/amd64	12911314	11351339	-13,74%
netbsd/arm	11463006	9875376	-16,08%
openbsd/386	11459942	9919602	-15,53%
openbsd/amd64	12919687	11407653	-13,25%
windows/386	11484160	10405888	-10,36%
windows/amd64	12846080	11665920	-10,12%

THE CLI IS NOT BACKWARD COMPATIBLE.