fix(friends-requests): improved requests and notifications display

[ThomBos]

What this PR does 📖
Fixed friends requests display
Which issue(s) this PR fixes 🔨
AP-1954

Special notes for reviewers 🗒️

Additional comments 🎤
Still missing some data to show (name and image, just when the other user hasn't accepted the request)

[ThomBos]

@josephmcg let me know what you think about these changes! 🔨

[josephmcg]

a couple ideas regarding FriendsManager state structure. If we switched details and requests to arrays, it would simplify a lot of this logic and improve Vue reactivity

[josephmcg]

would it be simpler to wrap the error creating methods in a try/catch (or promise.catch if async)?

[ThomBos]

Quick recap:

• all states are now arrays instead of objects, removed details state because it's now stored into list
• requestSave clears non-pending requests and sends requests change events using requestSendUpdate
• removeFriend is disconnected from requestSendUpdate (but it does basically the same thing) because 'accepted' or 'rejected' requests are no more stored in the state
• removed unused functions

Errors management is still in progress and has to be improved. 🔨
At the moment i'm thinking of adding a new state to contain an error string, so the components can render as it changes.
This would cause all "throw" to be removed, in order to remove all try/catches around the app...

Any suggestion to improved this code are well welcomed!! 💥🚀

we can come back to smaller things like this on cleanup, this pr is a good one to build off of