generic.go: GenericContainer(): clearer error message (#2327)

It's customary to prefix an actual Go error with a generic message explaining the error context.

Ir looks like it's already done this way everywhere [1] else in the code base, but not here.

[1] https://github.com/search?q=repo%3Atestcontainers%2Ftestcontainers-go%20%22failed%20to%20start%20container%22&type=code

container_test.go

@@ -320,7 +320,7 @@ func Test_GetLogsFromFailedContainer(t *testing.T) {
 		Started:          true,
 	})
 
-	if err != nil && err.Error() != "container exited with code 0: failed to start container" {
+	if err != nil && err.Error() != "failed to start container: container exited with code 0" {
 		t.Fatal(err)
 	} else if err == nil {
 		terminateContainerOnEnd(t, ctx, c)

generic.go

@@ -79,7 +79,7 @@ func GenericContainer(ctx context.Context, req GenericContainerRequest) (Contain
 
 	if req.Started && !c.IsRunning() {
 		if err := c.Start(ctx); err != nil {
-			return c, fmt.Errorf("%w: failed to start container", err)
+			return c, fmt.Errorf("failed to start container: %w", err)
 		}
 	}
 	return c, nil