Update CI to prevent merging any prints to stdout

[stevenroose]

                #[cfg(feature = "std")]
                debug_assert!({
                    println!("txid={} skip={}", txid, skip);
                    true
                });

this piece of code in tx_graph.rs prints out stuff when run in dev profile. That's pretty annoying tbh, I don't think it's uncommon for people to use CLIs in the dev profile and this messes up with stdout for these CLIs.

I reckon this has something to do with debugging, but I think there must be better ways to get these kinds of printouts without bothering users?

[LLFourn]

I think we should add to ci that:

rg 'dbg!|println!' -g '!*tests*' -g '!*examples*' -g '*.rs' crates

Should always show up clean

[ValuedMammal]

This might actually be fixed in #1194

[notmandatory]

Ya I did remove this debug_assert! in #1194 but if someone wants to remove it sooner in another PR that's fine by me.

[oleonardolima]

I tried a different approach on #1425, using both print_stdout and print_stderr lints, instead of adding a new step on the CI, wdyt @LLFourn @notmandatory ?