fix: update shellcheck/shfmt handling and set-up

Notably:

- We now always provide our own copies of both `shellcheck` and `shfmt` (via `get_sources.sh`)
- Set-up of the pre-commit hook is now at `lint-hook.sh`, so we can call it directly (and give users a way to set-up the hook directly if necessary)
- The `lint` CI stage is now performed on Fedora instead of Alpine (like the rest of the build process), but only the minimal set-up is performed to download and set-up the necessary tools

Signed-off-by: celenity <celenity@celenity.dev>

scripts/git-hooks/pre-commit

@@ -3,7 +3,7 @@
 # IronFox pre-commit hook: lints staged shell scripts with shellcheck + shfmt.
 #
 # Enabled by pointing git at this directory (done automatically by
-# scripts/bootstrap.sh):
+# scripts/lint-hook.sh):
 #   git config core.hooksPath scripts/git-hooks
 #
 # This is a convenience only. It can be bypassed with `git commit --no-verify`,