[TypeScript] Implement MultiLanguageLG in LocaleTemplateManager

[Batta32]

Related to #2489

Purpose

What is the context of this pull request? Why is it being done?
Update LocaleTemplateManager to use MultiLanguageLG, while also fixing an issue when the locale has upper cases.

Changes

Are there any changes that need to be called out as significant or particularly difficult to grasp? (Include illustrative screenshots for context if applicable.)

Bot Solutions SDK

• Update package.json to use botbuilder-lg@4.8.0-preview
• Update LocaleTemplateManager with the implementation of MultiLanguageLG
• Update the method onTurn of setLocaleMiddleware to set i18next language to lower case.

Sample Assistant and Sample Skill

• Fix Sample Skill copy-templates script to also copy the .lg files in the reponses folder
• Add botbuilder-lg@4.8.0preview dependency for tests
• Update the index file to use the updated LocaleTemplateManager
• Add the new AllResponses.lg files in both samples
• Update the .lg files to use $ instead of @ when using string templates
• Fix tests

Generator

• Fix Sample Skill copy-templates script to also copy the .lg files in the reponses folder
• Apply the same changes of the index file
• Apply the same changes of the response folder

Tests

Is this covered by existing tests or new ones? If no, why not?
Yes, it's covered by all the existing tests in each solution

Documentation

Update the document related to the migration of a Bot (VA/Skill) to implement the GA changes

Feature Plan

Are there any remaining steps or dependencies before this issue can be fully resolved? If so, describe and link to any relevant pull requests or issues.
-

Checklist

General

• I have commented my code, particularly in hard-to-understand areas
• I have added or updated the appropriate tests
• I have updated related documentation

[Batta32]

@darrenj - we already fixed the merge conflicts 😊!