This uses the newly introduced conditional configuration checks that are
now configurable withint Cargo (beta).
This allows us to get rid of our custom python script that checks for
expected features and cfgs.
This does introduce a warning regarding the unknown lint in Cargo
versions prior to the current beta, but since these are not rustc errors,
they won't break any builds with the "-D warnings" RUSTFLAG.
Moving to this lint actually exposed the "strict" feature not being
present in the lightning-invoice crate, as our python script didnt
correctly parse the cfg_attr where it appeared.
Rather than using the std benchmark framework (which isn't
maintained and is unlikely to get any further maintenance), we swap
for criterion, which at least gets us a variable number of test
runs so our benchmarks don't take forever.
We also fix the RGS benchmark to pass now that the file in use is
stale compared to today's date.
While `rapid-gossip-sync` recently gained a `no-std` feature, it
didn't actually work, as there were still dangling references to
`std` and prelude assumptions. This makes `rapid-gossip-sync`
build (and test) properly in `no-std`.
