Update Dockerfile samples to use MCR images

[dlepow]

Purpose

Update sample Dockerfiles to pull Microsoft first party image from Microsoft Container Registry instead of from Docker Hub.

Does this introduce a breaking change?

[ ] Yes
[ x] No

Should not be a breaking change. Testing is recommended.

Pull Request Type

What kind of change does this Pull Request introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ x] Refactoring (no functional changes, no api changes)
[ ] Documentation content changes
[ ] Other... Please describe:

How to Test

• Get the code

git clone [repo-address]
cd [repo-name]
git checkout [branch-name]
npm install

• Test the code

What to Check

Verify that the following are valid

• ...

Other Information

Please contact danlep (MSFT alias) if you have questions about this change. Thanks very much!