feat: deprecate the legacy workflow and recommend the new one

[DimitarTachev]

These changes are fully deprecating the Legacy Development Workflow and preparing the users for removing the its support in NativeScript 6.0.0.

PR Checklist

• The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/CONTRIBUTING.md#commit-messages.
• There is an issue for the bug/feature this PR is for. To avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it.
• You have signed the CLA.
• All existing tests are passing: https://github.com/NativeScript/nativescript-cli/blob/master/CONTRIBUTING.md#contribute-to-the-code-base
• Tests for the changes are included.

What is the current behavior?

We are fully supporting both the legacy prepare (copying the whole app folder and post-processing it with nativescript-dev-typescript, nativescript-dev-sass, etc.) and the webpack approach (using nativescript-dev-webpack and its plugins/loaders).

What is the new behavior?

We are deprecating the legacy workflow as shown on the charts below:

Related to: #4548

[DimitarTachev]

test cli-smoke#latest

[DimitarTachev]

test cli-smoke

[KristianDD]

The warning looks weird on Windows. Please check it before merge.

[elmissouri16]

@DimitarTachev I didn't work with native script for a year now I installed the latest version and i create with tns create app_name --js and when i run it i got this
"You are using the Legacy Workflow" im using windows any reason for it

[DimitarTachev]

@elmissouri16 I suppose you are using the next version of the CLI as this warning is not released in the official (latest) version yet.

You are getting the warning because the official app templates are not released with the new workflow. In order to switch to the recommended workflow before the official release, you can run tns update --workflow in your existing apps.

P.S. Bear in mind that this command is available only in nativescript@next. You could also switch the workflow by manually following the useLegacyWorkflow update described in this blog post .

[elmissouri16]

@DimitarTachev ok thanks lot I well try this out