Move opentelemetry-collector-builder into this repository

As a result of discussions in the SIG meeting and the conversation in this PR https://github.com/open-telemetry/opentelemetry-collector/pull/4199, it was decided the [opentelemetry-collector-builder](https://github.com/open-telemetry/opentelemetry-collector-builder) should be moved into this repo.