Update tests and examples after 2.0 Docker image release

[oeyh]

There are a few places where Data Prepper image with latest tag are pulled for e2e test and demo. This will likely break after 2.0 release and will need an update.

[dlvenable]

Data Prepper now supports major tags such as 1, 2. These point to the latest version in a major version series. I'd like to suggest that our examples make use of these tags. I think this provides a few benefits.

1. Our examples will not break when a major version is released
2. We will know what version of Data Prepper any given sample is using.

The downside is that we will need to update these version numbers after major version releases. But, I see this as a relatively small problem. If there are no breaking changes for any given sample, it is quite trivial. If there are breaking changes, we'd still have to change the configuration regardless of using latest or the major version tag.

[dlvenable]

@oeyh , Do you know if this is complete or not?

[oeyh]

@dlvenable This is closed via https://github.com/opensearch-project/data-prepper/pull/2019