std.crypto: handle the top bit in 25519.field.fromBytes64() (#9435)
std.crypto: handle the top bit in 25519.field.fromBytes64() (#9435)

The only known use case for this is the hash-to-curve operation where the top bit is always cleared.

But the function is public, so let's make it work as one would expect in the general case.

Also fix the comment by the way.
zig-lang/zig,zig-lang/zig,zig-lang/zig,andrewrk/zig,andrewrk/zig