Entities with long lineage lists cause 414 errors in rest.li

[gabe-lyons]

Describe the bug
When an entity attempts to fetch its lineage, datahub-frontend issues a batch-get call to gms with each entity urn in the url. If the entity has too many downstream or upstream dependencies, this URI can exceed rest.li's limit.

There is a way to send batch gets to rest.li via post:
https://linkedin.github.io/rest.li/Send-Rest_li-Request-Query-In-Request-Body

However, this does not seem to be supported by the generated rest.li client. We have opened an issue on rest.li's github to resolve this: linkedin/rest.li#603

To Reproduce
Steps to reproduce the behavior:

1. Create an entity with 100+ downstream dependencies
2. Attempt to view that entity in the react app

Expected behavior
This should load as expected

[shirshanka]

Fixed by #2462