chore(lint): enable gosec (#7792)

Enable "gosec" linter.

Exclude:

- All G115 (integer overflow) findings, to be fixed separately.

Add targeted gosec annotations for:

- non-crypto math/rand usage
- md5 used only for file change detection
- G114 ("net/http serve with no timeout settings"), to be fixed
  separately.

Other findings fixed.

Signed-off-by: Ville Vesilehto <ville@vesilehto.fi>

plugin/dnstap/io.go

@@ -70,6 +70,7 @@ func (d *dio) dial() error {
 
 	if d.proto == "tls" {
 		config := &tls.Config{
+			// #nosec G402 -- optional, user-configurable escape hatch for environments that cannot validate certs.
 			InsecureSkipVerify: d.skipVerify,
 		}
 		dialer := &net.Dialer{