[IMPROVE] Fetch members from API endpoint

[gerzonc]

Proposed changes

Currently we've been using a method call for fetching members, on RoomMembersView, but we should use REST API like the Web client does.

Issue(s)

How to test or reproduce

In order to test this you should create a group, direct message with multiple users or team, and server version being at least 3.16.0

1. Go to a room
2. Tap on room's title
3. Tap on Members

It should render the members that are online from that room

Screenshots

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• Improvement (non-breaking change which improves a current function)
• New feature (non-breaking change which adds functionality)
• Documentation update (if none of the other choices apply)

Checklist

• I have read the CONTRIBUTING doc
• I have signed the CLA
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works (if applicable)
• I have added necessary documentation (if applicable)
• Any dependent changes have been merged and published in downstream modules

Further comments

[lgtm-com]

This pull request introduces 1 alert when merging 4eeb478 into 2c31fc2 - view on LGTM.com

new alerts:

• 1 for Potentially inconsistent state update

[diegolmello]

lgtm