Fix warnings added over the last 3 years

[GnomedDev]

I also removed the clippy::pedantic and clippy::nursery warnings as those would take ages to fix up, when I just want to get the project into a workable state to update dependencies.

[sile]

Thank you for your PR. It looks good to me.
Although the CI test has failed, it doesn't appear to be caused by your changes. So, I will go ahead and merge this PR. I will address the test failure in a separate PR.