Batch retrieval of pipeline connections count on streams page.

[dennisoelkers]

Description

Motivation and Context

Prior to this PR, the streams page called an endpoint for each stream to retrieve the number of connected pipelines. This leads to running into the limit for concurrent requests quite fast. Also, it returns a 404 when no pipelines are connected, leading to retries and further delays.

This PR is speeding up the page by:

• Creating an API endpoint that returns a Map of stream ids -> pipelines for a given list of stream ids
• Uses a batcher in the frontend to bundle up individual requests to fetch connected pipelines, so only a single request is fired

/nocl No user-facing change.

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (non-breaking change)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.

[ousmaneo]

LGTM!

[kodjo-anipah]

LGTM