Bring SQL Server 2025 vector/JSON out of preview

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We've merged support for various SQL Server 2025 functionality that's still in preview; the relevant APIs generally have [Experimental] on them. These features should come out of preview on the SQL Server side before we release 11, so we should do the necessary adjustments on the EF side when that happens:

• VECTOR_SEARCH(). The syntax will likely change here (TOP_N removal for pre-filtering support).
• CREATE VECTOR INDEX.
• JSON_CONTAINS() (both the Contains translation and the EF.Function.JsonContains() translation. Specifically check what happens with a null item, a JSON item, an array item - these are currently unsupported, but if they are, we can unlock new translations via them (e.g. Contains over structural type collection (not just primitive), array-contained-within-array).