[DOCS] Work around for titleabbrev errors

[lcawl]

Summary

Related to elastic/docs#756

This PR works around elastic/docs#760 by adding a substitutions attribute for abbreviated titles that contain attributes. Otherwise, they are not resolved by Asciidoctor builds. For example:

[skip ci]

Checklist

Use strikethroughs to remove checklist items you don't feel are applicable to this PR.

- [ ] This was checked for cross-browser compatibility, including a check against IE11
- [ ] Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support

• Documentation was added for features that require explanation or tutorials
  - [ ] Unit or functional tests were updated or added to match the most common scenarios
  - [ ] This was checked for keyboard-only and screenreader accessibility

For maintainers

• This was checked for breaking API changes and was labeled appropriately
• This includes a feature addition or change that requires a release note and was labeled appropriately

[elasticmachine]

Pinging @elastic/kibana-docs

[schersh]

LGTM. To confirm, any page that uses an attribute in the title will need to add [subs="attributes"] under the header? @gchaps and I should keep an eye out for these, I think there are more out there. Do you run into any issues backporting this far?

[lcawl]

To confirm, any page that uses an attribute in the title will need to add [subs="attributes"] under the header?

Only pages that use attributes within <titleabbrev>. I'm cleaning up all occurrences I've found, but yes, it's something to keep an eye out for.

[lcawl]

Backported to 6.7 and earlier via d985a0a