fix(link/perf_event): ensure both perf link and perf event FDs are always closed

[maheshbhatiya73]

Summary

perfEventLink.Close() previously returned early if closing the link FD failed,
skipping cleanup of the underlying perf event (pl.pe). This caused:

• Perf event file descriptor leaks
• Stale tracefs events
• Potential resource exhaustion in long-running programs

Changes

This patch ensures that both resources are always closed, collecting all
errors using Go 1.20+ errors.Join:

func (pl *perfEventLink) Close() error {
    var errs []error
    if err := pl.fd.Close(); err != nil {
        errs = append(errs, fmt.Errorf("perf link close: %w", err))
    }
    if pl.pe != nil {
        if err := pl.pe.Close(); err != nil {
            errs = append(errs, fmt.Errorf("perf event close: %w", err))
        }
    }
    return errors.Join(errs...)
}

[lmb]

Couple of questions:

1. Have you seen this in problem in production?
2. Did you make this PR using an AI coding tool?