(feat) optimize Uniswap connector

[vic-en]

https://github.com/CoinAlpha/hummingbot/issues/3040

• Added zeroReserveCheckInterval
• Increased TTL
• Refactored update_pair function to update info about pairs in parallel
• Refactored some variables to the environment file

[dennisocana]

Merging instead of closing so we have a PR corresponding to the story #3040 in this release. Same changes are also in this commit https://github.com/CoinAlpha/gateway-api/pull/37/commits/c70b37c33888ef06b90d949c3c46b74391c1b3fa.