Improve performance of the JIRA macros

Currently, xwiki.org is calling heavily jira.xwiki.org, sometime threatening it's quality of service, or making in unavailable.

Early analysis

The jira macro rightfully does not have a cache, allowing it to quickly reflect changes on jira issues on wiki pages.

• It might be possible to rely on If-Modified-Since headers (if supported by the endpoint)
• we could change the endpoint to avoid relying on search when targeting a known set of IDs
• we could also use a robust jira client library that would abstract away the caching