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/updater/loop/state.go

@@ -2,7 +2,6 @@ package loop
 
 import (
 	"context"
-	"errors"
 	"fmt"
 	"reflect"
 	"sync"
@@ -31,8 +30,6 @@ func (l *Loop) GetStatus() (status models.LoopStatus) {
 	return l.state.status
 }
 
-var ErrInvalidStatus = errors.New("invalid status")
-
 func (l *Loop) SetStatus(ctx context.Context, status models.LoopStatus) (outcome string, err error) {
 	l.state.statusMu.Lock()
 	defer l.state.statusMu.Unlock()
@@ -79,8 +76,8 @@ func (l *Loop) SetStatus(ctx context.Context, status models.LoopStatus) (outcome
 		l.state.status = newStatus
 		return status.String(), nil
 	default:
-		return "", fmt.Errorf("%w: %s: it can only be one of: %s, %s",
-			ErrInvalidStatus, status, constants.Running, constants.Stopped)
+		return "", fmt.Errorf("invalid status: %s: it can only be one of: %s, %s",
+			status, constants.Running, constants.Stopped)
 	}
 }