Make `Hash.fromUniversalHashCode` null safe

[durban]

Similarly to how Show.fromToString have been recently made null safe (#4689 and #4790), I propose making Hash.fromUniversalHashCode also null safe. Specifically, I think it should use x.## instead of x.hashCode(). (The eqv method is already fine, as it uses ==.)

[LSUDOKO]

hi @durban
i would like to work on this issue can you assign me ??

[armanbilge]

Hi @LSUDOKO! before we assign you the issue, would you mind making a contribution to our onboarding repository? Directions are in the README.

https://github.com/typelevel/gsoc-onboarding

[LSUDOKO]

Hi @LSUDOKO! before we assign you the issue, would you mind making a contribution to our onboarding repository? Directions are in the README.

https://github.com/typelevel/gsoc-onboarding

yes, sure

[arnavsharma990]

Hi @armanbilge , I recently completed the onboarding contribution.
I'd like to work on this issue if it's available also I've gone through (#4689 and #4790 ) to understand the approach taken there.

[mattjliu]

Hi, I'd be curious to know if I need to have contributed to the onboarding repo to be assigned this issue, as I'm not a GSoC applicant and the deadline has passed.

If that's not the case I'd be happy to work on this. Thanks.

[armanbilge]

Hi @mattjliu that requirement was just for GSoC applicants! Thanks for your interest :)