Migrate kafkaexporter from Collector core to Collector contrib

[Saber-W]

Description:
This PR migrates the kafkaexporter component from the Collector core repository to the Collector contrib repository.

This PR retains the commit history from core and includes plumbing fixes for go.mod, makefile, components.go.

Link to tracking Issue:
opentelemetry-collector/#3474
opentelemetry-collector/#3649

[alolita]

Hi @bogdandrutu @tigrannajaryan based on our discussion last week, we're starting to file PRs to move each core component to contrib. Please review and merge. Thanks!

[bogdandrutu]

Please make sure you use the new translator module that you created for opencensus/jaeger if needed instead of the one in collector.

[anuraaga]

I'd recommend writing a pinned issue describing this migration effort, what/why/how. In particular, I just noticed the approach of copying the opentelemetry-core repo into internal/core in advance to then start integrating, which is a neat trick. But documenting this for reviewer benefit and also to keep a record for future archaeology is important. There is #3474, if it's an appropriate issue for this, than I would suggest rewriting the first comment in the issue to include details and the linked issues, etc, presenting it for users. /cc @alolita

It's unfortunate that the commit message in c713647, which is what will show up in git blame for years to come, is basically empty - that one deserved a lot of detail. At the least though GitHub links it to the PR which links to #3474 so we can at least flesh that issue out.