fix: avoid displaying users without metadata nor messages [WBP-1073]

[V-Gira]

Issue

• 1 on 1 conversations with users without metadata or messages still appear if the conversation is hosted on the selfuser b-e

Solution

• speciffically filter out conversations with users without metadata that do not have messages from the visible Conversations state

Additional steps

• the messages array isn't kept in memory outside active conversations, we added a hasContentMessages KO observable to conversation state to keep track of conversation with messages
• conversations were filtered for established mls conversations at the component level (and missing from the group folder component), refactored to the ConversationsState level

[codecov]

Codecov Report

Merging #15319 (ed9124f) into dev (78763ef) will increase coverage by 0.00%.
The diff coverage is 80.00%.

@@           Coverage Diff           @@
##              dev   #15319   +/-   ##
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  Coverage   43.18%   43.19%           
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  Files         647      647           
  Lines       21775    21779    +4     
  Branches     5004     5006    +2     
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+ Hits         9404     9407    +3     
- Misses      11167    11168    +1     
  Partials     1204     1204