Improve support for requests for large numbers of records from the pool_txs endpoint

[benwolski]

• The current limit on requests for pool transactions is set at 200. We should test performance at a higher limit (e.g. 400) and increase if possible.

https://ambindexer.net/gcgo/pool_txs?chainId=0x5&base=0x0000000000000000000000000000000000000000&quote=0xD87Ba7A50B2E7E660f678A895E4B72E7CB4CCd9C&poolIdx=36000&n=201