(feat) standard endpoints & consolidate protocol library functions

[gyozajiro]

• merge balancer & uniswap endpoint to under /eth
• consolidate functions on balancer, uniswap swaps price lookup
• cache swap pool as class property
• replace token contract address with token symbol on request param
• add mainnet token list (1inch)
• add maxswaps, ethGasStation api, gas level param to .env

[gyozajiro]

API Endpoints are consolidated as below:

General Ethereum API

# get ethereum-based wallet balances
/eth/balances

# get token allowance amount
/eth/allowances

# approve token allowance amount
/eth/approve

# get tx status update
/eth/poll

Balancer/Uniswap API

# initiate swap pool, auto-approve allowance
eth/{protocol}/start

# lookup buy/sell price
eth/{protocol}/price

# execute buy/sell trade
eth/{protocol}/trade

Terra API

# 
terra/start
terra/price
terra/trade

Import Postman collection & environment file in test/postman/v2 for latest endpoints and request params

[gyozajiro]

Client PR for this feature. https://github.com/CoinAlpha/hummingbot/pull/2905.

[dennisocana]

Requesting review from @vic-en as well so he can work on the story https://github.com/CoinAlpha/hummingbot/issues/3037

[PtrckM]

• using the config1

• no problem on subsequent orders

• however using this config2

• resulting with Fail with error 'UniswapV2Router: EXCESSIVE_INPUT_AMOUNT'

• also the history are incorrect on uniswap/balancer side

• different behavior on balancer using config3

-logs config1 config2 (uniswap) logs_doonconf.log logs_uniswap.log

-logs config3 balancer logs_ditomobile.log

[PtrckM]

• not able to run gateway, tried on different node versions v10.22.0, v10.22.1 and v10.23.1 all fails. Both mainnet and kovan fails

• able to run on both commit e354cbecaac8f6da93f424f453125acf9c462244 and 658429896355eaae3e3a4a0dd3a064f9c2a06e9d without any problems.

[PtrckM]

• fix issue where gateway can't start

• suggested UNISWAP_ALLOWED_SLIPPAGE=1.5