feat: add Chroma to the integration tests

[Laurianti]

Fixes #179

Adds Chroma to the databases of the integration tests: SupportedDatabase.Chroma, a chromadb/chroma:1.5.9 container started like the OpenSearch one, and [TestCase(SupportedDatabase.Chroma)] on the 7 tests of DatabaseTests, which all pass.

The Chroma row of the README now names CommunityToolkit.VectorData.Chroma: Microsoft.SemanticKernel.Connectors.Chroma still uses the v1 API (#179).

Chroma runs on CommunityToolkit.VectorData.Chroma, the Chroma provider of the AI Community Toolkit (CommunityToolkit/AI#58), built on ChromaDotNet.Client. These tests already use CommunityToolkit.VectorData.InMemory from the same toolkit. I maintain ChromaDotNet.

ChromaDotNet.Client is also used by the Chroma integrations of the Aspire Community Toolkit (CommunityToolkit/Aspire#2219, merged).

To run the Chroma tests, with Docker running:

cd src
dotnet test IntegrationTests/LangChain.Databases.IntegrationTests.csproj --filter "FullyQualifiedName~DatabaseTests&Name~Chroma"

[CLAassistant]

All committers have signed the CLA.

[Copilot]

Copilot review overview

🟢 Approval recommended

The Chroma setup is complete, API-compatible, and consistently integrated into the existing test infrastructure.

Review effort: Balanced
Findings: None

What changed in this PR

Adds Chroma 1.5.9 to the shared vector-store integration test suite using ChromaDotNet.VectorData.

Changes:

• Adds Chroma as a supported database and configures its container.
• Adds the Chroma vector-store dependency.
• Runs all seven vector-store integration tests against Chroma.

File	Description
src/​IntegrationTests/​SupportedDatabase.cs	Adds the Chroma database option.
src/​IntegrationTests/​LangChain.Databases.IntegrationTests.csproj	References the Chroma provider.
src/​IntegrationTests/​DatabaseTests.cs	Enables Chroma across vector-store tests.
src/​IntegrationTests/​DatabaseTests.Configure.cs	Starts and configures Chroma 1.5.9.
src/​Directory.Packages.props	Pins ChromaDotNet.VectorData 0.4.1.

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[Laurianti]

@HavenDV when you have a moment, could you approve the workflow run? I'd like to see the Chroma tests pass in the CI too.

Microsoft.SemanticKernel.Connectors.Chroma, the package the README names for Chroma today, is now deprecated on NuGet, with CommunityToolkit.VectorData.Chroma as the alternative. This PR moves the README row to that package.

The same holds for LangChain.Databases.Chroma 0.17.0, which fails with Chroma 1.x (#179) and whose source is no longer in this repository. Would you consider deprecating it on NuGet, with CommunityToolkit.VectorData.Chroma as the alternative package?