System.Diagnostics.DiagnosticSource 4.6.0-preview.x

#### Is your question related to a specific version? If so, please specify:
Azure Functions v2

#### What language does your question apply to? (e.g. C#, JavaScript, Java, All)
C#

#### Question
Hey there, over on the Azure SDK team we are running into some problems using the new preview versions of our libraries within the Azure functions host because it overrides the version of ```System.Diagnostics.DiagnosticSource``` that we are using.

Specifically our libraries require access to the Activity.IdFormat property which is not present in the version of ```System.Diagnostics.DiagnosticSource``` which is loaded into the Azure Functions v2 host.

Wondering what plans you have - if any for upgrading.

Link to issue in the .NET repo for the Azure SDK where this dependency has been identified as an issue: https://github.com/Azure/azure-sdk-for-net/issues/7354

Start by reviewing the Azure Functions v2 host's loaded System.Diagnostics.DiagnosticSource version and the linked Azure SDK issue (#7354). Determine whether the host can use a version exposing Activity.IdFormat; done means establishing and documenting an upgrade path that supports the Azure SDK preview libraries.

Written by the indexing model from the issue text.