feat(medusa): variants expand inventory_items (#4203)

* add expand params for inventory items to product and variant endpoints in store

* add changeset

* update integration test naming

* make priceSeelctionParams extends findParams and adjust api accordingly

.changeset/quiet-flowers-prove.md

@@ -0,0 +1,5 @@
+---
+"@medusajs/medusa": patch
+---
+
+feat(medusa): add allowed relation to expand params for product and variant endpoints