MM-12389 Update segment library to v3 (#11472)

* Update analytics-go dependency

* Migrate from segment library v2 to v3

* Reinclude gorilla/handlers module

* Fix missing module

* Remove reference to outdated analytics module

vendor/github.com/segmentio/analytics-go/timeout_15.go

@@ -0,0 +1,16 @@
+// +build !go1.6
+
+package analytics
+
+import "net/http"
+
+// http clients on versions of go before 1.6 only support timeout if the
+// transport implements the `CancelRequest` method.
+func supportsTimeout(transport http.RoundTripper) bool {
+	_, ok := transport.(requestCanceler)
+	return ok
+}
+
+type requestCanceler interface {
+	CancelRequest(*http.Request)
+}