goipgrep: refactor into module; pure-Go ping/resolve; cache+CI; drop binary

projects/go-tools/go/goipgrep/internal/resolve/neigh_unsupported.go

@@ -0,0 +1,23 @@
+//go:build !linux
+
+package resolve
+
+import "fmt"
+
+type NeighborTable struct {
+	ByMAC map[string][]string
+}
+
+type MACResolution struct {
+	MAC string   `json:"mac"`
+	IPs []string `json:"ips,omitempty"`
+}
+
+func LoadNeighborTable() (*NeighborTable, error) {
+	return nil, fmt.Errorf("MAC neighbor/ARP resolution is only supported on Linux without external tools")
+}
+
+func ResolveMACs(macs []string) ([]MACResolution, error) {
+	_ = macs
+	return nil, fmt.Errorf("MAC resolution is only supported on Linux without external tools")
+}