Implement rarity stats for levels

[BitTim]

Each level should have two rarity stats. A global one, including all non-private Valolink accounts and a friends one, which only includes friend accounts.

The stats are calculated by getting the number of accounts that have unlocked the level and dividing it by the number of all accounts. The result is the percentage of accounts that have unlocked the level. The progress bar shown should display the inverted percentage (The more the progress bar is filled, the rarer the level is)

nUnlocked / nTotal = rarity
displayedRarity = 1 - rarity

[BitTim]

This statistic will only be available when connected to the internet to avoid caching the user data of all users. This also means that a special query can be executed on the Supabase database directly