Historically, the headers have been bumped some time after a file has
been touched. Do it now to avoid having to touch them again in the
future for that reason.
-BEGIN VERIFY SCRIPT-
sed -i --regexp-extended 's;( 20[0-2][0-9])(-20[0-2][0-9])? The Bitcoin Core developers;\1-present The Bitcoin Core developers;g' $( git show --pretty="" --name-only HEAD~1 )
-END VERIFY SCRIPT-
In theory this commit should only touch the span.h header, because
std::span can implicilty convert into Span in most places, if needed.
However, at least when using the clang compiler, there are some
false-positive lifetimebound warnings and some implicit conversions can
not be resolved.
Thus, this refactoring commit also changed the affected places to
replace Span with std::span.
This removes the ability for BIP324Cipher to generate its own key, moving that
responsibility to the caller (mostly, V2Transport). This allows us to write
the random-key V2Transport constructor by delegating to the explicit-key one.
