Add descriptions for more cat APIs

[lcawl]

This PR pulls descriptions from these docs:

• https://www.elastic.co/guide/en/elasticsearch/reference/master/cat-nodeattrs.html
• https://www.elastic.co/guide/en/elasticsearch/reference/master/cat-nodes.html
• https://www.elastic.co/guide/en/elasticsearch/reference/master/cat-pending-tasks.html
• https://www.elastic.co/guide/en/elasticsearch/reference/master/cat-plugins.html
• https://www.elastic.co/guide/en/elasticsearch/reference/master/cat-recovery.html
• https://www.elastic.co/guide/en/elasticsearch/reference/master/cat-repositories.html

[github-actions]

Following you can find the validation results for the APIs you have changed.

API	Status	Request	Response
cat.master	🟢	1/1	1/1
cat.nodeattrs	🟢	5/5	5/5
cat.nodes	🟢	11/11	11/11
cat.pending_tasks	🟢	1/1	1/1
cat.plugins	🟢	2/2	2/2
cat.recovery	🟢	6/6	6/6
cat.repositories	🟢	6/6	6/6

You can validate these APIs yourself by using the make validate target.