1) Added special handling for the extension to resolve the dependency.

2) Added 'is_sys_obj' to the ignore list of Schema Diff.
3) Font awesome v5 fixes.

web/pgadmin/static/scss/_alertify.overrides.scss

@@ -200,7 +200,6 @@
 
 .pg-alertify-icon-button {
   &:before {
-    font-size: 1.1em !important;
     line-height: 1.2;
     font-family: $font-family-icon;
     font-weight: 900;

web/pgadmin/static/scss/_webcabin.pgadmin.scss

@@ -34,6 +34,10 @@
   display: flex;
   border-radius: $btn-border-radius;
   margin: auto;
+
+  & .pg-font-icon {
+    line-height: unset;
+  }
 }
 
 /* darken % taken from bootstrap - button_variant */
@@ -167,7 +171,7 @@
   padding: 0rem 0.75rem;
 
   &.fa, &.pg-font-icon{
-    padding: 0rem 0.25rem 0rem 0rem
+    padding: 0rem 0.25rem 0rem 0rem;
   }
 }