[Multiple Datasource] Help menu should include link to the documentation guide

[joshuarrrr]

When reviewing #3685, I noticed that the only in-application link to the multiple datasource documentation (https://opensearch.org/docs/latest/dashboards/discover/multi-data-sources/) is in the experimental callout, which will go away when the feature goes to GA in 2.7.0.

That guide is a great resource - we should also add it to the help menu for the data source management plugin pages.

[joshuarrrr]

CC @zhongnansu - If we have time, I'd love to include this in the 2.7 scope.

[zhongnansu]

@shanilpa Please take a look, if it makes sense we could consider adding this to our roadmap.

[joshuarrrr]

For now, I'll bump the label to 2.9.0, since it's not assigned yet.

[joshuarrrr]

ha, nvm, thanks @zhongnansu

[seraphjiang]

@zhongnansu is it still valid?

[zhongnansu]

@zhongnansu is it still valid?

@seraphjiang
Yes, it's valid. After out of experimental, we removed the banner and , we no longer have a doc link for multiple datasource feature from the application. If we want to add it, we need to figure a place on the data source management page to add it. I'll take a look at where and how other features/plugins are adding documentation link