CSV report (saved search@dashboard): defer to the dashboard panel's selection of fields, not the fields in saved search data

[0asp0]

Kibana version: 7.3.1

Elasticsearch version: 7.3.1

Server OS version: Windows 10

Browser version: Vivaldi

Browser OS version: Windows 10

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

Describe the bug:
If I use a different configuration on saved search and on dashboard, then the selected fields of saved search are used instead of the shown fields on dashboard.

example:

saved search: field hostname is selected.
saved search embedded on dashboard: ipAddress is selected.
I expect to see timestamp and ipIddress in csv when exporting on dashboard level. But the csv contains timestamp and hostname. It doesn't matter if I save the dashboard or if I do the column changes without saving. But I expect that it should work without saving.

Steps to reproduce:

1. create a save search and select hostname field for being displayed
2. save search as "test"
3. create dashboard and add saved search test to it.
4. save dashboard
5. change shown columns on dashboard any other field (e.g. IP)
6. hit Download CSV button

Expected behavior:
csv file contains timestamp and IP
but csv file contains timestamp and hostname (seems to be taken from saved search)

Errors in browser console (if relevant):

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

Any additional context:
discussion: https://discuss.elastic.co/t/feedback-on-csv-export-of-saved-search-in-dashboard/196748

[elasticmachine]

Pinging @elastic/kibana-stack-services

[tsullivan]

This fix might be achievable now with some of the new enhancements to the saved search information in our SearchEmbeddable. See #43634

[tsullivan]

This will be addressed when CSV Export uses SearchSource on the server internally. This is a priority since it is related to supporting Runtime Fields with CSV Export: #81079

[elasticmachine]

Pinging @elastic/kibana-app-services (Team:AppServices)

[elasticmachine]

Pinging @elastic/kibana-reporting-services (Team:Reporting Services)

[tsullivan]

This has not been addressed yet: at the time of writing #81079 the APIs were not available to use the "unsaved" set of columns in the request.

I'm going to close this though, as a duplicate of #18439