Make system info button text selectable in firefox (#7559)

core/src/main/resources/lib/hudson/property-table.css

@@ -4,6 +4,7 @@
 
 .app-hidden-info-hide > button {
   text-align: left;
+  user-select: text;
 }
 
 span.jenkins-\!-color-blue > svg {

core/src/main/resources/lib/hudson/property-table.js

@@ -12,8 +12,14 @@
       .querySelectorAll(".app-hidden-info-hide .jenkins-button")
       .forEach(function (elem) {
         elem.addEventListener("click", function () {
-          elem.parentElement.classList.add("jenkins-hidden");
-          elem.parentElement.previousSibling.classList.remove("jenkins-hidden");
+          const selection = window.getSelection();
+          // Don't hide value while it's being selected
+          if (selection === null || window.getSelection().type !== "Range") {
+            elem.parentElement.classList.add("jenkins-hidden");
+            elem.parentElement.previousSibling.classList.remove(
+              "jenkins-hidden"
+            );
+          }
         });
       });