p2p/dnsdisc: add implementation of EIP-1459 (#20094)

This adds an implementation of node discovery via DNS TXT records to the
go-ethereum library. The implementation doesn't match EIP-1459 exactly,
the main difference being that this implementation uses separate merkle
trees for tree links and ENRs. The EIP will be updated to match p2p/dnsdisc.

To maintain DNS trees, cmd/devp2p provides a frontend for the p2p/dnsdisc
library. The new 'dns' subcommands can be used to create, sign and deploy DNS
discovery trees.

vendor/github.com/cloudflare/cloudflare-go/errors.go

@@ -0,0 +1,50 @@
+package cloudflare
+
+// Error messages
+const (
+	errEmptyCredentials     = "invalid credentials: key & email must not be empty"
+	errEmptyAPIToken        = "invalid credentials: API Token must not be empty"
+	errMakeRequestError     = "error from makeRequest"
+	errUnmarshalError       = "error unmarshalling the JSON response"
+	errRequestNotSuccessful = "error reported by API"
+	errMissingAccountID     = "account ID is empty and must be provided"
+)
+
+var _ Error = &UserError{}
+
+// Error represents an error returned from this library.
+type Error interface {
+	error
+	// Raised when user credentials or configuration is invalid.
+	User() bool
+	// Raised when a parsing error (e.g. JSON) occurs.
+	Parse() bool
+	// Raised when a network error occurs.
+	Network() bool
+	// Contains the most recent error.
+}
+
+// UserError represents a user-generated error.
+type UserError struct {
+	Err error
+}
+
+// User is a user-caused error.
+func (e *UserError) User() bool {
+	return true
+}
+
+// Network error.
+func (e *UserError) Network() bool {
+	return false
+}
+
+// Parse error.
+func (e *UserError) Parse() bool {
+	return true
+}
+
+// Error wraps the underlying error.
+func (e *UserError) Error() string {
+	return e.Err.Error()
+}