[CONFSERVER-25899] Add performance improvement by caching of static content via Apache mod_disk_cache - Create and track feature requests for Atlassian products.

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Pass on to customers what we have learned from the recent performance tuning on CAC, via the Apache mod_disk_cache.

DONE: Add a new page as child of "Running Confluence behind Apache", called Configuring Apache to Cache Static Content via mod_disk_cache
https://confluence.atlassian.com/display/DOC/Configuring+Apache+to+Cache+Static+Content+via+mod_disk_cache

DONE: Add links to the new page from these pages:
- https://confluence.atlassian.com/display/DOC/Performance+Tuning – just mention this tip in particular, and point to relevant docs.
- https://confluence.atlassian.com/display/DOC/Configuring+a+Large+Confluence+Installation – just mention this tip in particular, and point to relevant docs.
- https://confluence.atlassian.com/display/DOC/Cache+Performance+Tuning – just mention this tip in particular, and point to relevant docs.
- https://confluence.atlassian.com/display/DOC/Running+Confluence+behind+Apache – just mention this tip in particular, and point to relevant docs.

relates to

CONFCLOUD-25899 Add performance improvement by caching of static content via Apache mod_disk_cache