[Feature Request] All validation delegates should be async and return a validation result

[jmprieur]

Why?

• We want to avoid the sync over async
• We don't want to throw when there are several authentication schemes

What?

Add more delegates that are async and result a validation result

Size: XL in Wilson, SAL, MISE.

Open Issue: RSA is not async ... we'll have to have async to sync,

[pmaytak]

Will fix #2556, #468