Fleet policy output fields disabled in Basic subscription without explanation

[runejuhl]

Kibana version: 8.5.2

Elasticsearch version: N/A

Server OS version: N/A

Browser version: N/A

Browser OS version: N/A

Original install method (e.g. download page, yum, from source, etc.): N/A

Describe the bug:

When configuring Fleet policy outputs the form fields are disabled, and there is not indication as to why this is, as shown in the screenshot below:

This caused me quite a bit of frustration and cost me some time, as I initially suspected that the Fleet output configuration itself was to blame.

Adding a help text to the form when the subscription doesn't allow configuring Fleet policy outputs would have prevented this.

Steps to reproduce:

1. Install and configure Elasticsearch, Kibana and Fleet using the Basic (free) subscription
2. Try to change Fleet output per Fleet policy

Expected behavior:

A help text should be shown when the form fields are disabled due to subscription.

Screenshots (if relevant):

Errors in browser console (if relevant):

Provide logs and/or server output (if relevant):

Any additional context:

I'm not well versed in modern (JS-based) web development, but I imagine
that something like I've done in runejuhl@24fc434 could do the trick. Let me know if you want me to open a PR.

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)