[NFC] Templatize `makeBlock` so it can be used with any iterable (#5583)

Replace the different overloads we previously had for different kinds of
containers with generic templates. We still need dedicated overloads for
`std::initializer_list` because it is never inferred in a template context,
though. Also, since `std::initializer_list` does not allow subscripting, update
the arena vector implementation to use iterators instead now that initializer
lists can be passed down to that layer without being reified as vectors.

1 files changed, 3 insertions, 2 deletions

diff --git a/src/mixed_arena.h b/src/mixed_arena.h
index a36f72a8d..4d8cda0ac 100644
--- a/src/mixed_arena.h
+++ b/src/mixed_arena.h
@@ -253,8 +253,9 @@ public:
     if (allocatedElements < size) {
       static_cast<SubType*>(this)->allocate(size);
     }
-    for (size_t i = 0; i < size; i++) {
-      data[i] = list[i];
+    size_t i = 0;
+    for (auto elem : list) {
+      data[i++] = elem;
     }
     usedElements = size;
   }