LibSQL+SQLServer: Implement first cut of SELECT ... ORDER BY foo

Ordering is done by replacing the straight Vector holding the query
result in the SQLResult object with a dedicated Vector subclass that
inserts result rows according to their sort key using a binary search.
This is done in the ResultSet class.

There are limitations:
- "SELECT ... ORDER BY 1" (or 2 or 3 etc) is supposed to sort by the
n-th result column. This doesn't work yet
- "SELECT ... column-expression alias ... ORDER BY alias" is supposed to
sort by the column with the given alias. This doesn't work yet

What does work however is something like
```SELECT foo FROM bar SORT BY quux```
i.e. sorted by a column not in the result set. Once functions are
supported it should be possible to sort by random functions.

Userland/Libraries/LibSQL/AST/Select.cpp

@@ -7,6 +7,7 @@
 #include <LibSQL/AST/AST.h>
 #include <LibSQL/Database.h>
 #include <LibSQL/Meta.h>
+#include <LibSQL/ResultSet.h>
 #include <LibSQL/Row.h>
 
 namespace SQL::AST {
@@ -77,6 +78,14 @@ RefPtr<SQLResult> Select::execute(ExecutionContext& context) const
         }
     }
 
+    bool has_ordering { false };
+    AK::NonnullRefPtr<TupleDescriptor> sort_descriptor = AK::adopt_ref(*new TupleDescriptor);
+    for (auto& term : m_ordering_term_list) {
+        sort_descriptor->append(TupleElementDescriptor { .order = term.order() });
+        has_ordering = true;
+    }
+    Tuple sort_key(sort_descriptor);
+
     for (auto& row : rows) {
         context.current_row = &row;
         if (where_clause()) {
@@ -93,7 +102,17 @@ RefPtr<SQLResult> Select::execute(ExecutionContext& context) const
                 return context.result;
             tuple.append(value);
         }
-        context.result->append(tuple);
+
+        if (has_ordering) {
+            sort_key.clear();
+            for (auto& term : m_ordering_term_list) {
+                auto value = term.expression()->evaluate(context);
+                if (context.result->has_error())
+                    return context.result;
+                sort_key.append(value);
+            }
+        }
+        context.result->insert(tuple, sort_key);
     }
     return context.result;
 }