[6.1] Fixes build issues for AKV Provider

[cheenamalhotra]

Link to successful non-official build: Build 150340

[Copilot]

Pull request overview

This PR updates build/signing conditions and OneBranch pipeline templates to address AKV Provider build and publishing flow issues, primarily by keying signing behavior off SigningKeyPath and improving AKV pipeline orchestration.

Changes:

• Switch strong-name signing conditions in SqlClient (netfx/netcore, src/ref) and AKV Provider projects to be driven by SigningKeyPath presence rather than CDP_BUILD_TYPE.
• Update OneBranch AKV build templates to support parameterized ReferenceType and to use the repo artifacts/ output paths consistently.
• Enhance AKV build job to optionally download the just-built MDS NuGet artifact and add it as a local NuGet source before building the AKV Provider.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/Microsoft.Data.SqlClient/netfx/src/Microsoft.Data.SqlClient.csproj	Gate signing and InternalsVisibleTo based on SigningKeyPath instead of CDP_BUILD_TYPE.
src/Microsoft.Data.SqlClient/netfx/ref/Microsoft.Data.SqlClient.csproj	Gate reference-assembly signing based on SigningKeyPath.
src/Microsoft.Data.SqlClient/netcore/src/Microsoft.Data.SqlClient.csproj	Gate signing and InternalsVisibleTo based on SigningKeyPath instead of CDP_BUILD_TYPE.
src/Microsoft.Data.SqlClient/netcore/ref/Microsoft.Data.SqlClient.csproj	Gate reference-assembly signing based on SigningKeyPath.
src/Microsoft.Data.SqlClient/add-ons/AzureKeyVaultProvider/Microsoft.Data.SqlClient.AlwaysEncrypted.AzureKeyVaultProvider.csproj	Gate AKV Provider signing based on SigningKeyPath.
eng/pipelines/onebranch/steps/compound-publish-symbols-step.yml	Adjust symbols folder path to point to repo artifacts/ output location.
eng/pipelines/onebranch/steps/compound-extract-akv-apiscan-files-step.yml	Adjust source folder paths for copying AKV DLL/PDB from artifacts/.
eng/pipelines/onebranch/steps/compound-build-akv-step.yml	Add referenceType parameter and adjust logging/tree output to artifacts/.
eng/pipelines/onebranch/sqlclient-official.yml	Pass softwareFolder/symbolsFolder for apiscan extraction and provide mdsArtifactName to AKV job.
eng/pipelines/onebranch/sqlclient-non-official.yml	Pass softwareFolder/symbolsFolder for apiscan extraction and provide mdsArtifactName to AKV job.
eng/pipelines/onebranch/jobs/build-akv-official-job.yml	Use artifactDirectory, add optional MDS artifact download + local NuGet source, and wire referenceType as 'Package'.