Performance: Optimize refresh of hybrid cache for a document by retrieving draft and published in single query

[AndyButland]

Description

It was noted that GetContentSourceAsync is called more than once during save and publish operations, and that we go to the database both for published and draft content even though the data returned is the same.

I first tackled this with use of a request cache in #21282, but I think the approach in this PR is cleaner.

When refreshing the memory cache, both draft and published versions need to be fetched. Previously this required two separate database calls. Since both versions come from the same row in the cmsContentNu table, this optimization fetches the ContentSourceDto once and creates both cache nodes from it.

Change Summary

• Adds GetContentSourceForPublishStatesAsync method to IDatabaseCacheRepository that retrieves both draft and published ContentCacheNode in a single database query
• Refactors DocumentCacheService.RefreshMemoryCacheAsync to use the new method, reducing database round-trips from 2 to 1

Testing

I've added a further integration test to verify this change RefreshMemoryCache_Fetches_Draft_And_Published.

[Copilot]

Pull request overview

This PR optimizes the RefreshMemoryCacheAsync method to fetch both draft and published content in a single database query instead of making two separate calls.

Changes:

• Adds GetContentSourceForPublishStatesAsync method to fetch both draft and published versions in one query
• Refactors DocumentCacheService.RefreshMemoryCacheAsync to use the new optimized method
• Includes default interface implementation for backward compatibility with a V18 TODO to remove it

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
src/Umbraco.PublishedCache.HybridCache/Persistence/IDatabaseCacheRepository.cs	Adds new interface method with default implementation for backward compatibility
src/Umbraco.PublishedCache.HybridCache/Persistence/DatabaseCacheRepository.cs	Implements optimized method and refactors existing code to extract shared database query logic
src/Umbraco.PublishedCache.HybridCache/Services/DocumentCacheService.cs	Updates RefreshMemoryCacheAsync to use the new optimized method
tests/Umbraco.Tests.Integration/Umbraco.PublishedCache.HybridCache/DocumentHybridCacheMockTests.cs	Adds test coverage and mock setup for the new method

[nikolajlauridsen]

Looks great to me! And I agree that it's cleaner than a request cache 👍

I did a minor minor edit, just changing a couple of == null to is null for consistency.