Maps app needs to tell users which privileges they need to upload geoJSON in layers

[bhavyarm]

Kibana version: 8.0.0

Elasticsearch version: 8.0.0

Browser version: chrome latest

Browser OS version: os x

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

Describe the bug: If user with "global_,maps_all" tries to upload geoJSON file - maps app displays a blank screen in layers panel.

Steps to reproduce:

1. Create an user with "all privileges" for maps in a space role and login with that user - make sure they have write access for data
2. Go to maps app + try to upload a file in geoJSON layers
3. The action doesn't go through and maps display a blank screen on side panel

Expected behavior: Maps app should tell the user clearly what roles are required to upload the file.

Screenshots (if relevant):

Errors in browser console (if relevant):

Uncaught (in promise) TypeError: indexes.map is not a function
    at getExistingIndexNames (indexing_service.js:247)
    at async IndexSettings.loadExistingIndexData (index_settings.js:26)
getExistingIndexNames @ indexing_service.js:247
:5620/api/maps/fileupload/import:1 Failed to load resource: the server responded with a status of 400 (Bad Request)
fatal_errors_service.tsx:96 Detected an unhandled Promise rejection.
TypeError: Cannot read property 'length' of undefined
wizard.tsx:70 Uncaught (in promise) TypeError: Cannot read property 'length' of undefined
    at wizard.tsx:70
    at JsonUploadAndParse._indexData (json_upload_and_parse.js:155)
(anonymous) @ wizard.tsx:70
(anonymous) @ json_upload_and_parse.js:155
:5620/api/maps/fileupload/import:1 Failed to load resource: the server responded with a status of 400 (Bad Request)
fatal_errors_service.tsx:96 Detected an unhandled Promise rejection.
TypeError: Cannot read property 'length' of undefined
wizard.tsx:70 Uncaught (in promise) TypeError: Cannot read property 'length' of undefined
    at wizard.tsx:70
    at JsonUploadAndParse._indexData (json_upload_and_parse.js:155)
(anonymous) @ wizard.tsx:70
(anonymous) @ json_upload_and_parse.js:155
6

[elasticmachine]

Pinging @elastic/kibana-gis (Team:Geo)

[nreese]

closing, duplicate of #41885