Composite products disappear on category pages during reindex for huge catalogs

According to current architecture, there is a possible situation that composite products will disappear for some time during inventory reindex.
Thinks become worse since 2.4.0, because stock status for products is taken from index table.

### Preconditions
1. Magento 2.3.5
2. Huge catalog (or set sleep in plugins to \Magento\InventoryIndexer\Indexer\SourceItem\Strategy\Sync)

### Steps to reproduce
1. Open category - see products (configurable and bundle).
2. Run reindex and wait until simple product will be reindexed and indexer will be busy with configurable/bundle reindex (or just wait with sleep)
3. Flush cache.
4. Open same category.

### Expected result (*)
1. Nothing changed. Products still appears on the category.

### Actual result (*)
1. No products are shown. Products will appear only after reindex finish.

The root cause of the problem is because switch happened before composite products are being reindexed.
https://github.com/magento/inventory/blob/265905238a467813363003f8ec29f7cbae5e1c33/InventoryIndexer/Indexer/Stock/Strategy/Sync.php#L148

Start with InventoryIndexer/Indexer/Stock/Strategy/Sync.php around line 148 and reproduce the category-page behavior during a large-catalog reindex, using the listed sleep-based setup if needed. Trace when the switch occurs relative to configurable and bundle reindexing; done means composite products remain visible while reindexing is still in progress.

Written by the indexing model from the issue text.