When using ProductSync with multiple ProductDrafts that reference product types, the library may issue multiple duplicate requests to fetch all product types.

[aqaexplorer]

Describe the bug
ProductTypeServiceImpl.fetchCachedProductAttributeMetaDataMap(productTypeId) checks:

if (productsAttributesMetaData.isEmpty()) { return fetchAndCacheProductMetaData(productTypeId); }
On the very first calls, the cache is still empty.
Each concurrent (or even sequential but fast) call triggers its own QueryUtils.queryAll(...).
Because the caching happens asynchronously, subsequent calls still see the cache as empty until the first queryAll finishes.
As a result, multiple identical full queries for product types are executed.

To Reproduce
Steps to reproduce the behavior:
Call sync with multiple ProductDrafts that reference product types

Expected behavior
The first call should trigger one asynchronous cache warm-up.
All subsequent calls (while the warm-up is in progress) should wait for the same future instead of starting new queries.