resizable: Inline some function in apfl_resizable_append

Profiling revealed that this gets called quite a lot

src/resizable.c

@@ -215,15 +215,28 @@ apfl_resizable_splice(
 bool
 apfl_resizable_append(struct apfl_allocator allocator, size_t elem_size, void **mem, size_t *len, size_t *cap, const void *other_mem, size_t other_len)
 {
-    return apfl_resizable_splice(
+    if (other_len == 0 || other_mem == NULL) {
+        return true;
+    }
+
+    if (!apfl_resizable_ensure_cap_for_more_elements(
         allocator,
         elem_size,
         mem,
-        len,
-        cap,
         *len,
-        0,
-        other_mem,
+        cap,
         other_len
+    )) {
+        return false;
+    }
+
+    memcpy(
+        ((char *)(*mem)) + *len * elem_size,
+        other_mem,
+        other_len * elem_size
     );
+
+    *len += other_len;
+
+    return true;
 }