[Fleet] Add support for installing tag saved objects

[joshdover]

Fleet integrations are planning to add tags to installed Kibana assets like Dashboard and Visualizations to identify the specific integration they're related to and to tag them as "managed" by the system elastic/integrations#327

We need to add support to the EPM installation and upgrade code to support install these SO types.

On the client side it's recommended to use the SavedObjectTagging client instead of the default SavedObjectsClient, but there currently is no analog API for the server-side. @pgayvallet any reason we'd have problems with using the regular SOC.bulkCreate or SOC.import APIs for this use case?

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)

[pgayvallet]

On the client side it's recommended to use the SavedObjectTagging client instead of the default SavedObjectsClient, but there currently is no analog API for the server-side

I didn't add it because it wasn't required when we initially implemented tagging, but we could easily expose the TagsClient from the server-side savedObjectTagging's start contract if necessary.

any reason we'd have problems with using the regular SOC.bulkCreate or SOC.import APIs for this use case?

The main upside of using the dedicated client is the validation performed on the tag's property. Now, the tag client isn't doing any kind of transformations, so using bulkCreate should be fine.

Also , import is already used to import tags from SOM (as the type is exportable), so you wouldn't be doing anything new by leveraging this API.

In short: imho it's fine to use bulkCreate or import