Fix fragment corruption in the GlobalOrderWriter

Previously there was an issue with the GlobalOrderWriter when using a
maximum fragment size. If we resumed a write where the first tile would
cause the partially written fragment to overflow the set maximum size,
we failed to check that a single tile could fit. This resulted in a
convoluted path where `dim_tiles[-1].cell_num()` return a reasonable
result (instead of segfaulting or throwing an exception).

This lead us to writing the wrong `last_tile_cell_num` value in the
FragmentMetadata. When reading the last tile from one of these corrupted
fragments, the logic in `Tile::load_chunk_data` would throw an exception
when the expected size was calculated off an invalid
`last_tile_cell_num` which caused an exception to be thrown and rendered
the last tile of the fragment unreadable.

The fix is simply to make sure we check if a single tile can fit and if
not, to create a new fragment. For a belt and suspenders approach to
safety, we've also changed the code in `WriterBase::set_coords_metadata`
to use `std::vector::at` instead of `std::vector::operator[]` so that
bounds checking is performed and assertion is thrown rather than writing
a bad FragmentMetadata to disk.

test/regression/targets/sc-34072.cc

@@ -53,7 +53,7 @@ TEST_CASE("Global Order Writer Resume Writes Bug", "[global-order-writer][bug][s
   // `std::vector::at` which does bounds checking. This causes us to throw
   // an exception in `WriterBase::set_coords_metadata` instead of silently
   // setting the last tile cell number to some garbage value.
-  REQUIRE_THROWS(query.submit());
+  REQUIRE(query.submit() == Query::Status::COMPLETE);
 
   array.close();
 }

tiledb/sm/query/writers/global_order_writer.cc

@@ -801,6 +801,14 @@ Status GlobalOrderWriter::global_write() {
     // Compute the number of tiles that will fit in this fragment.
     auto num = num_tiles_to_write(idx, tile_num, tiles);
 
+    // If we're resuming a fragment write and the first tile doesn't fit into
+    // the previous fragment, we need to start a new fragment and recalculate
+    // the number of tiles to write.
+    if (current_fragment_size_ > 0 && num == 0) {
+      RETURN_CANCEL_OR_ERROR(start_new_fragment());
+      num = num_tiles_to_write(idx, tile_num, tiles);
+    }
+
     // Set new number of tiles in the fragment metadata
     auto new_num_tiles = frag_meta->tile_index_base() + num;
     throw_if_not_ok(frag_meta->set_num_tiles(new_num_tiles));