Fix prev/next links on public profile page (#6497)

* Fix prev/next links on public profile page

* Don't make pagination urls if no available statuses

* Fix empty check method

* Put left chevron before prev page link

* Add scope for pagination "starting at" a given id

* Status pagination try 2:

s/prev/older and s/next/newer
"older" on left, "newer" on right
Use new scope for "newer" link
Extract magic 20 page size to constant
Remove max_id from feed pagination as it's not respected

* Reinstate max_id for accounts atom stream

* normalize

app/javascript/styles/mastodon/accounts.scss

@@ -233,8 +233,8 @@
 
   a,
   .current,
-  .next,
-  .prev,
+  .newer,
+  .older,
   .page,
   .gap {
     font-size: 14px;
@@ -257,13 +257,13 @@
     cursor: default;
   }
 
-  .prev,
-  .next {
+  .older,
+  .newer {
     text-transform: uppercase;
     color: $ui-secondary-color;
   }
 
-  .prev {
+  .older {
     float: left;
     padding-left: 0;
 
@@ -273,7 +273,7 @@
     }
   }
 
-  .next {
+  .newer {
     float: right;
     padding-right: 0;
 
@@ -295,8 +295,8 @@
       display: none;
     }
 
-    .next,
-    .prev {
+    .newer,
+    .older {
       display: inline-block;
     }
   }