1e62350ca2 refactor: Improve use of explicit keyword (Fabian Jahr)
c502a6dbfb lint: Use c++17 std in cppcheck linter (Fabian Jahr)
Pull request description:
I found the `extended-lint-cppcheck` linter still uses `std=c++11` when reviewing #20471. The only difference in the output after this change is one line is missing:
```
src/script/descriptor.cpp:159:5: warning: Struct 'PubkeyProvider' has a constructor with 1 argument that is not explicit. [noExplicitConstructor]
```
After some digging, I am still not sure why this one is ignored with c++17 when 40 other`noExplicitConstructor` warnings were still appearing.
In the second commit, I fix these warnings, adding `explicit` where appropriate and adding fixes to ignore otherwise.
ACKs for top commit:
practicalswift:
cr ACK 1e62350ca2: patch looks correct!
MarcoFalke:
review ACK 1e62350ca2
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