feat: [SUB-BRANCH] Implement channel list of players and counter

[sandrade-dcl]

What does this PR change?

Fix #2735

In order to know who are you talking with within channels, players need a way to know the number of players connected to the same channel.

The players will be listed in a new section, accessible by a button in the channel conversation view. The channels will display the number of connected players next to their name in the conversations list view.

Figma design: https://www.figma.com/file/SxxomcIZI1zyytMZmFJAvS/Social-Improvements?node-id=3303%3A39380 Data Flow: https://hackmd.io/sMgwddkUR_SDZvWqLlFfeg?view#Ability-to-get-the-list-of-users-joined-to-a-channel

How to test the changes?

1. Go to: https://play.decentraland.org/?renderer-branch=feat/implement-channel-list-of-players-and-counter&kernel-branch=feat/add-friends-lazy-load
2. Join any channel.
3. Expand the new members section.
4. Notice a list of users are loaded.

Our Code Review Standards

https://github.com/decentraland/unity-renderer/blob/master/docs/code-review-standards.md

[github-actions[bot]]

After the CI passes:

• This branch can be previewed at https://play.decentraland.zone/?renderer-branch=feat/implement-channel-list-of-players-and-counter
• Code coverage report: https://renderer-artifacts.decentraland.org/branch-coverage/feat/implement-channel-list-of-players-and-counter
• Benchmark report: https://renderer-artifacts.decentraland.org/branch-benchmark/feat/implement-channel-list-of-players-and-counter/index.html

[lorux0]

The window fades out if i leave the mouse over the member list after a couple of seconds. The window should remain visible because the member list should be part of the focus area.