Speed up Utxo fetching

[rynoV]

• This is taking ~5-15 seconds on each page load (depending on how ogmios/cardano-node is feeling on the day, I guess)
• We're fetching all the utxos using ogmios via CTL's utxosAt
• The current method of fetching the utxos using ogmios (implemented by CTL) is being deprecated, and hopefully the new method of using a chain index will speed up this operation

[samuelWilliams99]

Seems this is blocked by the ongoing discussion of which index to use