v2: migrate contribs to new instrumentation api (2)

[rarguelloF]

What does this PR do?

Migrate contribs to new instrumentation api:

• confluentinc/confluent-kafka-go
• confluentinc/confluent-kafka-go.v2
• database/sql
• dimfeld/httptreemux.v5
• elastic/go-elasticsearch.v6
• emicklei/go-restful.v3
• gin-gonic/gin
• globalsign/mgo
• go.mongodb.org/mongo-driver

Motivation

Reviewer's Checklist

• Changed code has unit tests for its functionality at or near 100% coverage.
• System-Tests covering this feature have been added and enabled with the va.b.c-dev version tag.
• There is a benchmark for any new code, or changes to existing code.
• If this interacts with the agent in a new way, a system test has been added.
• Add an appropriate team label so this PR gets put in the right place for the release notes.
• Non-trivial go.mod changes, e.g. adding new modules, are reviewed by @DataDog/dd-trace-go-guild.

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