[PORT] Support accessing global memories in injecting LG templates as Expressions

[tomlm]

Port this change from botbuilder-dotnet/master branch:
microsoft/botbuilder-dotnet#4452

Issue reported by @chrimc62 that the injected LG function don't have access to global state (DSM state).

This PR enable injected LG template functions to access global memories.

Suppose we have a template, with a global variable {user: {name: "user1", date: "2001-01-01"}, }

> !# @strict = false
> !# @namespace = Adaptive
> !# @Exports = UserDataConcat

#UserDataConcat()
- ${user.name} : ${user.date}

The result of evaluating the expression Expression.parse("Adaptive.UserDataConcat()") is user1 : 2001-01-01

Changed projects

• Microsoft.Bot.Builder.LanguageGeneration
• Microsoft.Bot.Builder.Dialogs.Adaptive.Templates.Tests
• Microsoft.Bot.Builder.LanguageGeneration.Tests