run shellcheck on all files, other small pre-commit updates

[jameslamb]

Contributes to rapidsai/build-planning#135

Follow-up to #662

While reviewing #805 and #831, I found myself suggesting things manually that I know shellcheck would have caught automatically. To prevent that for reviewers in the future, this proposes running shellcheck on all shell scripts in the repo, not just those in the ci/ directory.

Other changes:

• updates rapids-dependency-file-generator to its latest version (1.18.1)
• consolidates duplicate entries for https://github.com/pre-commit/pre-commit-hooks in .pre-commit-config.yaml

[jameslamb]

/merge