Currently, many modules depend on `managed-ledger-test.jar` just because they want to use MockBookkeeper and MockZookeeper.  This made module dependencies hard to understand and track.

This PR introduces a new `testmocks` module and pulls all mocks from managed-ledger tests into the new module.

*Motivation*

Bump the development version to 2.6.0-SNAPSHOT

* Removed managed-ledger-shaded artifact

* Fixed dep artifact renaming error

Fixes #4791

**Motivation**

Currently the Pulsar Kafka wrapper is using Kafka 0.10.x version. However, there are users who use legacy-kafka version in their system and willing to move to pulsar. This PR provides pulsar-kafka adapter for kafka-api-version 0.9.X. So, this adapter can help users in their migration process from kafka-0.9 to pulsar.

* adding a module that shades managed-ledger

* removing commented out lines

Signed-off-by: NSijie Guo <sijie@apache.org>

* Updates headers with ASF source files header

* change license to additional files