Gasless contract using gas as normal contract

[ledanghuy1811]

Context

From v0.50.x, we set gasless for some contracts but when we executes functions of these contracts, gas used of these txs is larger than we expected

To Reproduce

Steps to reproduce the behavior:

1. Create a set-gasless contract proposal
2. Wait for proposal pass
3. Try to execute one of functions of contract
4. See error

Expected behavior

Gas used of this tx is smaller than usual

[ledanghuy1811]

The error that txs of these contracts still use more gas is because in function execute of wasm keeper, we check if contract is gasless contract then we set gas = 0 for context by WithGasMeter function. This function return new context for execution but after execute function is end, it seem like the process of execution still use old context, this lead to gas still large

[ledanghuy1811]

To fix this issue, we use RefundGas function to reduce gas used for gasless contract, this function doesn't return new context then after execution, the gas used is decreased for gasless contract