Fix txlist RPC endpoint to use the token info for fee currencies

[carterqw2]

Description

The txlist RPC endpoint uses the CeloParams table to fetch names of stable tokens used as gas currencies. The way the feeCurrency mapping is implemented is a bit cumbersome and requires manual population of the table with the parameters. It can take it from the Tokens table instead.

Before:

curl -s https://explorer.celo.org/mainnet/api\?module\=account\&action\=txlist\&address\=0xccc9576F841de93Cd32bEe7B98fE8B9BD3070e3D | jq '.' | grep -i "0xcb625dd58eb29e8df606276927375ea8aa9c983cb09812aa5784b5da28d6e149" -A 10 -B 10 | grep feeCurrency
      "feeCurrency": "CELO",

After:

curl -s https://explorer.celo.org/mainnet/api\?module\=account\&action\=txlist\&address\=0xccc9576F841de93Cd32bEe7B98fE8B9BD3070e3D | jq '.' | grep -i "0xcb625dd58eb29e8df606276927375ea8aa9c983cb09812aa5784b5da28d6e149" -A 10 -B 10 | grep feeCurrency
      "feeCurrency": "USDC",

[github-actions]

Unit Test Results

       5 files  ±0     363 suites  ±0   3m 40s ⏱️ -6s
2 636 tests ±0  2 562 ✔️ ±0  74 💤 ±0  0 ❌ ±0 
2 650 runs  ±0  2 574 ✔️ ±0  76 💤 ±0  0 ❌ ±0 

Results for commit d61d04f. ± Comparison against base commit 7cee218.

♻️ This comment has been updated with latest results.