Add saved objects bulkResolve API

[jportner]

Originally when we implemented SavedObjectsClient.resolve, we envisioned it to be used only in precise cases where a "deep link" URL is used. However, we recently discovered that initially, the usage of resolve will be more widespread than anticipated:

• Because of how embeddables are loaded by reference (Differentiate load-by-reference for embeddables #111191)
• Because of how the data plugin exposes index patterns data views to consumers (Improve data plugin handling of resolve #111196)

The client-side SavedObjectsClient silently takes get calls and batches them into bulkGet for performance reasons; this allows a Kibana page to load without making dozens or hundreds of separate HTTP calls to load all of the data that it needs.

Based on the two linked issues above, if we don't do the same for resolve, it could result in a very negative performance impact and/or cause Kibana pages to stop functioning entirely if the maximum open request limit is exceeded.

With that in mind, we need to:

1. Create a bulkResolve API, and
2. Change the client-side implementation to batch resolve calls into bulkResolve

[elasticmachine]

Pinging @elastic/kibana-security (Team:Security)