firefox: 89.0.2 -> 90.0

make gtk3Support non-optional, because it hasn't been for a long time
also make gtk2 conditional on firefox older than 90, because we can get
rid of it with firefox 90, but it's still needed by the current ESR
release

(cherry picked from commit b332794adf841262958424c623c442cc8fab92e8)

pkgs/applications/networking/browsers/firefox/no-buildconfig-ffx90.patch

@@ -0,0 +1,22 @@
+--- a/docshell/base/nsAboutRedirector.cpp
++++ b/docshell/base/nsAboutRedirector.cpp
+@@ -66,8 +66,6 @@ static const RedirEntry kRedirMap[] = {
+     {"about", "chrome://global/content/aboutAbout.html", 0},
+     {"addons", "chrome://mozapps/content/extensions/aboutaddons.html",
+      nsIAboutModule::ALLOW_SCRIPT},
+-    {"buildconfig", "chrome://global/content/buildconfig.html",
+-     nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT},
+     {"checkerboard", "chrome://global/content/aboutCheckerboard.html",
+      nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT |
+          nsIAboutModule::ALLOW_SCRIPT},
+--- a/toolkit/content/jar.mn
++++ b/toolkit/content/jar.mn
+@@ -39,8 +39,6 @@ toolkit.jar:
+    content/global/plugins.html
+    content/global/plugins.css
+    content/global/plugins.js
+-*   content/global/buildconfig.html
+-   content/global/buildconfig.css
+    content/global/contentAreaUtils.js
+    content/global/datepicker.xhtml
+ #ifndef MOZ_FENNEC