The logic here is that we can use one central session for all client actions.
Also, set the user agent for the *runtime* version of fwupd -- it's the runtime
version we use when checking capabilities, rather than the built-against
version. This would also explain why there are so many very obsolete versions
of fwupd being recorded on the LVFS...
Although we supported other hashes than SHA1 (which is now moderately unsafe)
we had to switch the metadata provider and daemon on some kind of flag day to
using SHA256. Since that's somewhat impractical, just allow multiple checksums
to be set on objects and just try to match whatever is given in preference
order.
This also means we can easily transition to other hash types in the future.
The removed API was never present in a tarball release, so not an API break.
