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

internal/configuration/settings/httpproxy.go

@@ -48,7 +48,7 @@ func (h HTTPProxy) validate() (err error) {
 	// Do not validate user and password
 	err = validate.ListeningAddress(h.ListeningAddress, os.Getuid())
 	if err != nil {
-		return fmt.Errorf("%w: %s", ErrServerAddressNotValid, h.ListeningAddress)
+		return fmt.Errorf("server listening address is not valid: %w", err)
 	}
 
 	return nil
@@ -176,7 +176,6 @@ func readHTTProxyLog(r *reader.Reader) (enabled *bool, err error) {
 	case "disabled", "no", "off":
 		return ptrTo(false), nil
 	default:
-		return nil, fmt.Errorf("HTTP retro-compatible proxy log setting: %w: %s",
-			ErrValueUnknown, value)
+		return nil, fmt.Errorf("HTTP retro-compatible proxy log setting: value is unknown: %s", value)
 	}
 }