SOLR-13665: Added missing netty dependencies to solrJ

[janhoy]

Description

ClassNotFound error when attempting SSL connection with the new Zookeeper 3.5.5.

Solution

Added missing netty dependencies to solrJ and upgraded netty to v 4.1.29.Final which is the version ZK uses.

See also https://issues.apache.org/jira/browse/ZOOKEEPER-3494. Probably the new Solr gradle build will "just work" from ZK 3.5.6 and later (for 3.5.5 we'd pull in netty-all which is unnecessarily large).

Tests

Hard to test since we do not have any ZK SSL tests in the code base

Checklist

Please review the following and check all that apply:

• I have reviewed the guidelines for How to Contribute and my code conforms to the standards described there to the best of my ability.
• I have created a Jira issue and added the issue ID to my pull request title.
• I am authorized to contribute this code to the ASF and have removed any code I do not have a license to distribute.
• I have given Solr maintainers access to contribute to my PR branch. (optional but recommended)
• I have developed this patch against the master branch.
• I have run ant precommit and the appropriate test suite.
• I have added tests for my changes.
• I have added documentation for the Ref Guide (for Solr changes only).

[janhoy]

Regarding RefGuide docs, this is handled in SOLR-7893