fix(dashboard): Load product variant edit page and fix product detail query key (#10029)

**What**
- Fixes Edit Variant form so it properly loads the product variant
- Fixes the query key for product details to prevent the cache from being shared between queries for the same ID but with different params.

Resolves CMRC-685

Co-authored-by: Frane Polić <16856471+fPolic@users.noreply.github.com>

.changeset/modern-walls-appear.md

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+---
+"@medusajs/dashboard": patch
+---
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+fix(dashboard): Fix query key for product details and load product variant data correctly