Improve BasicTable <caption> text

[alisonelizabeth]

Currently, the BasicTable component renders a caption with the text "Below is a table of X items."

eui/src/components/basic_table/basic_table.js

Line 470 in f33c710

default="Below is a table of {itemCount} items."

This isn't ideal if a page has multiple tables. It would be great if this text could be configurable or if the default could provide more context.

Suggested text from @barlowm:

"Below is the <table_name> table containing <number_of_visible_items> rows out of <number_of_total_items_if_multiple_pages>."

Related issue: elastic/kibana#43842

[myasonik]

Also, captions have role caption added to them which is not allowed and not officially supported.

(Search for "caption" on this W3C page to verify. Can also see the violation when running axe.)

[kobelb]

This is necessary to address the following Kibana accessibility issues:

• (Accessibility) Manage Users - Tables need better information kibana#43018
• (Accessibility) Spaces - Tables need better information kibana#42505
• (Accessibility) Kibana Stack Monitoring - Tables need better information kibana#42400