[Go] Feature request: detect unchecked CertPool.AppendCertsFromPEM output

We should trigger an error if the value returned from `AppendCertsFromPEM` is not checked:

```go
roots := x509.NewCertPool()
roots.AppendCertsFromPEM(caPEM)
```

See https://cs.opensource.google/go/go/+/refs/tags/go1.25.4:src/crypto/x509/cert_pool.go;l=219

The issue was found by Claude Code in my project.
