SOLR-15141: Remove V2RequestSupport SolrJ interface

[gerlowskija]

Description

V2RequestSupport was intended to allow support for v2 requests in SolrJ, but was never really adopted on a critical mass of SolrRequest implementations. Now that the v2 API has had more time to mature, there are better approaches for supporting v2 APIs in SolrJ.

Solution

Removes V2RequestSupport interface from SolrJ.

Tests

N/A

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 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 ./gradlew check.
• I have added documentation for the Ref Guide (for Solr changes only).