Changing uid gid

[pacostas]

Summary

The purpose of this PR is to set proper uids and gids on stack images.

Use Cases

Checklist

• [x] I have viewed, signed, and submitted the Contributor License Agreement.
• [ ] I have linked issue(s) that this PR should close using keywords or the Github UI (See docs)
• [x] I have added an integration test, if necessary.
• [x] I have reviewed the styleguide for guidance on my code quality.
• [x] I'm happy with the commit history on this PR (I have rebased/squashed as needed).

[sophiewigmore]

I'll take a look tomorrow!

[mhdawson]

In case people wonder about the reason for this.

1) our images are based on an existing image that used 1001 as the run image 2) when we originally tested out the nodejs-extension we used 1001 for both the build and run uids. During review it was suggested we be consistent with the rest of the buildpacks and use different uids. We did not know of any issue in doing that so modified to do that. 3) While @pacostas was running the existing integration tests againt the npm-install buildpack he discoverd a problem with permissions. 4) Swapping these uids in the way this PR does maintains the separation of using a different uid in the build and run phases while keeping the run uid consistent with what is used in the base images we are extending and resolves the permissions issues we ran into.

[sophiewigmore]

@pacostas changes look good, just need an update to the integration tests here because they are now failing