dev(SSJ): use OZ contracts

[obatirou]

Remove custom implementation (ownable and upgradeable) that were copy from OZ and add the OZ contract dependencies.

[manlikeHB]

Hi @obatirou, can I work on this?

[ClementWalter]

hey @manlikeHB sure, I assigned you

[manlikeHB]

Hi @ClementWalter, I realized SSJ contains a custom openzeppelin package which contains an ERC20 contract. Adding the the OZ dependency will cause a clash between the two.

Should I proceed to removing the custom openzeppelin package and use OZ's component for the ERC20 contract?

[obatirou]

Hi @ClementWalter, I realized SSJ contains a custom openzeppelin package which contains an ERC20 contract. Adding the the OZ dependency will cause a clash between the two.

Should I proceed to removing the custom openzeppelin package and use OZ's component for the ERC20 contract?

Yes, please do so
This is the goal of this issue: remove the custom OZ packages and use the official ones