fix: rid of UB and memory leak based on clang warnings

[knst]

• fixed UB with reading unitialized data from buffer and compare by memcmp
• fix: add missing final and virtual destructor to avoid memory leak.

It also removes several clang's warnings during build.

[PastaPastaPasta]

I think this should be done upstream

[knst]

I think this should be done upstream

• fix:UB with reading unitialized data in tests of "class PrivateKey" Chia-Network/bls-signatures#358
• fix: add missing destructor for CoreMPL and final for nested classes Chia-Network/bls-signatures#359

[github-actions]

'This PR has been flagged as stale due to no activity for over 60
days. It will not be automatically closed, but it has been given
a stale-pr label and should be manually reviewed.'

[knst]

@PastaPastaPasta that 2 PR are dead in Chia's repo.

Can you review and merge this PR instead waiting them get merged and backported later?

[PastaPastaPasta]

utACK for squash merge

[UdjinM6]

should backport Chia-Network#370 and Chia-Network#371

[UdjinM6]

superseded by #83