fix(medusa): Performance improvement for variant availability (#3921)

**What**
- refactor availability invocations to only do one call to the inventory module

@adrien2p would love to run through some tests of this with you and get your take on approach

.changeset/lazy-seas-wait.md

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+"@medusajs/medusa": patch
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+fix(medusa): update query performance for getting product and variant avaiability