Setup a samples repo as a submodule to make PR reviews easier

[baywet]

Darrel and I had further brainstorming on this and here is a recap.
We have multiple concerns here:

• The launch.json configuration should be valid, the paths should resolve with minimal repos cloning/rework from people cloning this repo.
• The parameters should be documented so people can configure other IDEs, use dotnet run, use a compiled version of kiota... getting started documentation #96
• The unit tests coverage should be ramped up and test aspects, not just generate files increase unit testing coverage to at least 80% of branches #79
• The PRs should provide a generation diff (more on that below)
• We want to avoid overcrowding this repo with too many things

The solution we're suggesting is the following:

• create a samples repo under the Microsoft Org, this repo will contain multiple projects (one for each language)
• add this repo as a submodule to kiota's repository
• update launch.json to point to this submodule's path

Someone PRing kiota to change the generation result should:

1. run the generation on the sample repo
2. create a PR in the generation repo
3. update the submodule reference
4. create the PR in Kiota, linking to that generation PR

This has the advantage of:

• providing a generation diff for reviewers
• not polluting the current repo
• force us to start building proper unit tests
• being simple for anyone who knows about submodules
• not being blocking for anyone who doesn't know about submodule

Thoughts?

Originally posted by @baywet in #48 (comment)
AB#9017

[baywet]

repo created https://github.com/microsoft/kiota-samples