Add `memoryReference` to evaluate response where possible

[jreineckearm]

Found as part of a PR on Memory Inspector to add support for "Show in Memory Inspector" from watch window: eclipse-cdt-cloud/vscode-memory-inspector#166 (comment)

For VS Code to set the canReadMemory context value to true for a watch window entry, the evaluate response needs to return a valid memoryReference property. See for example https://github.com/microsoft/vscode/blob/9ecd1e915b655f7c5d09fe4fa7fe908b930bc1e2/src/vs/workbench/contrib/debug/browser/watchExpressionsView.ts#L402

We should add this for better integration with that addition.

[omarArm]

done in #544