[WIP] Add localstack test to S3 package

[grouville]

Localstack test implementation.

As I didn't rebase frequently, I need to add the S3#Sync tonight, but currently stuck by the issues cited below.

I am encountering these 2 issues :

• A race condition (Through my tests/debugging, I realized that we cp / sync a file/ folder to AWS S3, then we query it right away with a recursive ls. However, it triggered an error (not very clear) that the file doesn't exist (fixed with a sleep, but if behavior is confirmed, will need to find a better fix). According to me, it was hidden by the fact that we used to always query pre-existing files.
• The tests totally work on my personal AWS accounts, but when using CI creds, it seems to break. Seen with Sam, but I don't know how to fix it.

Prerequisites :
For the LocalStack test to run, you need to have LocalStack running on port 4566 : pip install localstack, then localstack start. Once running, you also need to create the dagger-ci bucket : aws --endpoint-url=http://localhost:4566 s3 mb s3://dagger-ci.

[grouville]

@samalba, on the first run. The CI broke, but not related to AWS tests (Kubernetes and Docker Run) : ultra weird that it doesn't work locally using CI creds. If it works again, I'll wipe everything and start again with a clean setup

[aluzzardi]

@samalba, on the first run. The CI broke, but not related to AWS tests (Kubernetes and Docker Run) : ultra weird that it doesn't work locally using CI creds. If it works again, I'll wipe everything and start again with a clean setup

Yep, we've had CI issues, should be fixed now by rebasing.

NOTE: you'll need to remove random.cue if you created one and use dagger.io/random instead (just like in Kubernetes)