[DOCS] Add system & hidden indices definitions. (#64834)
[DOCS] Add system & hidden indices definitions. (#64834)

* [DOCS] Add system & hidden indices definitions.

* Update docs/reference/glossary.asciidoc

* Update docs/reference/glossary.asciidoc

Co-authored-by: Lisa Cawley <025a615f48e5f82ccd74faaae1bf263bd2374e6e@elastic.co>

* Update docs/reference/glossary.asciidoc

* Update docs/reference/glossary.asciidoc

Co-authored-by: Lisa Cawley <025a615f48e5f82ccd74faaae1bf263bd2374e6e@elastic.co>
nknize/elasticsearch,nknize/elasticsearch,robin13/elasticsearch,nknize/elasticsearch,GlenRSmith/elasticsearch,GlenRSmith/elasticsearch,robin13/elasticsearch,nknize/elasticsearch,robin13/elasticsearch,GlenRSmith/elasticsearch,GlenRSmith/elasticsearch,robin13/elasticsearch,robin13/elasticsearch,GlenRSmith/elasticsearch,nknize/elasticsearch