refactor: move WebGetTitle inside measurexlite (#895)

Part of https://github.com/ooni/probe/issues/2240

internal/measurexlite/web.go

@@ -0,0 +1,19 @@
+package measurexlite
+
+//
+// Code to process web results (e.g., from web connectivity)
+//
+
+import "regexp"
+
+// WebGetTitle returns the title or an empty string.
+func WebGetTitle(measurementBody string) string {
+	// MK used {1,128} but we're making it larger here to get longer titles
+	// e.g. <http://www.isa.gov.il/Pages/default.aspx>'s one
+	re := regexp.MustCompile(`(?i)<title>([^<]{1,512})</title>`)
+	v := re.FindStringSubmatch(measurementBody)
+	if len(v) < 2 {
+		return ""
+	}
+	return v[1]
+}