[7.x] Reduce number of indexed fields in index pattern saved object (#74817)

[mattkime]

Backports the following commits to 7.x:

• Reduce number of indexed fields in index pattern saved object (Reduce number of indexed fields in index pattern saved object #74817)

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: 1b19db0

Build metrics

Saved Objects .kibana field count

id	value	diff	baseline
index-pattern	3	-7	10

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream