Index Patterns Cannot Be Created for System Index-Only Cluster

[jonasll]

Kibana version:
7.9

Elasticsearch version:
7.9

Server OS version:
Elastic Cloud - GCP Iowa

Browser version:
Chrome 84.04

Browser OS version:
Mac OS X 10.15.3

Original install method (e.g. download page, yum, from source, etc.):
Elastic Cloud Deployment

Describe the bug:
Given a cluster with system indices and no user-generated indices, index patterns cannot be created.

Steps to reproduce:

1. Spin up an Enterprise Search Deployment or any Elasticsearch deployment with system indices only
2. Stack Management > Index patterns > Create Index Pattern
3. An error appears: Couldn't find any Elasticsearch data

Current Workaround
Creating a "bogus" index (e.g. test, or 123) seems to allow user to access the index creation view, where the system index toggle can be turned on for successful creation of index patterns.

Expected behavior:
For Enterprise Search deployments, all indices are created as system indices. The ability to visualize or review logs using Kibana requires index pattern creation.

Screenshots (if relevant):

[mattkime]

Addressed in the 7.10 index pattern creation redesign - #68819