ensure OSS builds receive notice of telemetry and link to opt-out

[LeeDr]

Kibana version: 7.5.0

Elasticsearch version: 7.5.0

Server OS version:

Browser version:

Browser OS version:

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

Describe the bug: When an OSS user upgrades from 7.4 (really anything prior to 7.5) to 7.5.0 telemetry becomes enabled and we don't show them a banner or message about how to opt out.

Steps to reproduce:

1. Install 7.4 Elasticsearch and Kibana
2. Load some data. Same data should do here because the splash screen in Kibana only shows up if there's no index pattern saved objects and it wouldn't be the normal case for someone to upgrade when they don't have any Kibana index patterns.
3. Upgrade to 7.5.0
4. Start Kibana and see if any banner or notification appears

Expected behavior: They should see the Opt In/Out banner message and buttons or the message on the splash screen.

Screenshots (if relevant):

Errors in browser console (if relevant):

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

Any additional context:

[elasticmachine]

Pinging @elastic/kibana-stack-services (Team:Stack Services)

[alexfrancoeur]

@joelgriffith While in here, we'll want to update the text on the new banner and splash screen to provide more concrete instructions for opting out since we cannot deep link / anchor

To learn about how usage data helps us manage and improve our products and services, see our Privacy Statement. To stop collection, disable usage data here.

I've bolded the changes. cc: @bmcconaghy

[joelgriffith]

@alexfrancoeur and @LeeDr this is now merged into master, backports are building. Not sure if you want to verify first before I remove this from our blockers?

[alexfrancoeur]

I realize that I'm probably too late here, but just took it for a spin on master.

I tested data without an index pattern. The splash screen shows notice and the saved object seems to be updated accordingly. ✅

I also tested with data and an index pattern. The notice is shown and the saved object is updated accordingly when I hit Dismiss ✅

LGTM, great work @joelgriffith and team!

[joelgriffith]

Thanks @alexfrancoeur! #50941 is now merged for 7.5