SOLR-17302: Convert /cluster filestore APIs to JAX-RS

[gerlowskija]

https://issues.apache.org/jira/browse/SOLR-17302

Description

Solr has slowly been modifying its v2 APIs to align around a more REST-ful model, implemented using the JAX-RS framework. Many APIs have already been through this re-alignment, but many more remain including Solr's filestore APIs (used internally by package store).

Solution

This commit migrates several of the filestore APIs, namely those under the /cluster/files path to use the JAX-RS framework. The APIs themselves are unchanged from an end-user perspective.

Other endpoints, particularly the "fetch filestore entry" (GET /api/node/files/somepath.txt) and "delete local filestore entry" (DELETE /api/node/files/somepath.txt) are not attempted in this PR, but left for another.

Tests

Existing filestore and package-store tests continue to pass.

Checklist

Please review the following and check all that apply:

• [x] I have reviewed the guidelines for How to Contribute and my code conforms to the standards described there to the best of my ability.
• [x] I have created a Jira issue and added the issue ID to my pull request title.
• [x] I have given Solr maintainers access to contribute to my PR branch. (optional but recommended)
• [x] I have developed this patch against the main branch.
• [x] I have run ./gradlew check.