#7447061 Jetpack Agency Dashboard: update empty state messages and hide/show search/filter

Proposed Changes

This PR makes the following changes

• Hide the search and filter when there are no sites found and no filter/search is applied.
• Update the empty state messages for different states.

Testing Instructions

Prerequisites

Since this change is made specifically for agencies, you must set yourself(partner) as an agency – 2c49b-pb. Make sure to switch it back to the previous type.

Instructions

1. Run git checkout update/empty-state-for-agency-dashboard and yarn start-jetpack-cloud
2. Open http://jetpack.cloud.localhost:3000/, and you’ll be redirected to the /dashboard.
3. Enter any text in the search box/apply a filter, verify the empty state messages are shown and filter/search is hidden when no sites are found and no search/filter is applied for the below scenarios

Scenarios

1. When no sites are found in the All tab and no filter/search is applied.

2. When no sites are found in the All tab and filter/search is applied.

3. When no sites are found in the Favorites tab and no filter/search is applied.

4. When no sites are found in the Favorites tab and filter/search is applied.

Pre-merge Checklist

Complete applicable items on this checklist before merging into the trunk. Inapplicable items can be left unchecked.

Both the PR author and reviewer are responsible for ensuring the checklist is completed.

• Have you written new tests for your changes?
• Have you tested the feature in Simple, Atomic, and self-hosted Jetpack sites?
• Have you checked for TypeScript, React or other console errors?
• Are we memoizing when appropriate (for expensive computations)? More info in Our Approach to Data and Memoizing with create-selector and Using memoizing selectors
• Have we sent any new strings for translation ASAP?

Related to 1202076982646589-as-1202537169533321 & 1202076982646589-as-1202578425954554