Move PropertyExtensions from Update to Metadata

[JoasE]

See: #37577 (comment)

[Copilot]

Pull request overview

This PR relocates the ConvertToProviderValue internal extension from the update pipeline to the metadata layer so it can be reused by other components (e.g., Cosmos serialization) without referencing the Update.Internal namespace.

Changes:

• Moved IProperty.ConvertToProviderValue(...) from Microsoft.EntityFrameworkCore.Update.Internal to Microsoft.EntityFrameworkCore.Metadata.Internal.
• Updated EFCore Update and EFCore.Cosmos call sites/usings to reference the new namespace.
• Removed the now-redundant src/EFCore/Update/Internal/PropertyExtensions.cs file.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/EFCore/Update/Internal/PropertyExtensions.cs	Removed old location of ConvertToProviderValue.
src/EFCore/Update/Internal/InternalUpdateEntryExtensions.cs	Switched to Microsoft.EntityFrameworkCore.Metadata.Internal to keep ConvertToProviderValue usage compiling.
src/EFCore/Metadata/Internal/PropertyExtensions.cs	Added ConvertToProviderValue implementation to the metadata internal extensions set.
src/EFCore.Cosmos/Query/Internal/CosmosSerializationUtilities.cs	Updated using to the new ConvertToProviderValue namespace for Cosmos serialization.

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