chore: do not use sentinel errors when unneeded

- main reason being it's a burden to always define sentinel errors at global scope, wrap them with `%w` instead of using a string directly
- only use sentinel errors when it has to be checked using `errors.Is`
- replace all usage of these sentinel errors in `fmt.Errorf` with direct strings that were in the sentinel error
- exclude the sentinel error definition requirement from .golangci.yml
- update unit tests to use ContainersError instead of ErrorIs so it stays as a "not a change detector test" without requiring a sentinel error

.golangci.yml

@@ -68,6 +68,9 @@ linters:
           - err113
           - mnd
         path: ci\/.+\.go
+      - linters:
+          - err113
+        text: "do not define dynamic errors, use wrapped static errors instead"
 
     paths:
       - third_party$