Update cppcheck

[goatgoose]

Problem:

The cppcheck build started failing, and was fixed in #5238. The workaround to get it building is not great though, and was added just to get the CI passing again. Ideally we would bump the cppcheck version to the latest release instead. However, this is a bigger change since it will require fixing many new suggestions the new version will have.

Solution:

Update cppcheck and fix any new suggestions that are raised.

[goatgoose]

We should check to see if there's a prebuilt github action for this.