feat: filter withdrawals by configured filters

[bendanzhentan]

This PR introduces 3 kinds of withdrawal filters, to filter out malicious withdrawals:

// WhitelistL2TokenList is the list of L2 tokens to whitelist for the L2StandardBridgeBot contract.
//
// L2StandardBridgeBot contract doesn't limit the L2 tokens to be bridged, but this off-chain bot
// process only whitelists the tokens in this list and ignore tokens not in this list.
//
// **IMPORTANT: If this list is unset (by default), all L2 tokens are whitelisted.**
WhitelistL2TokenList *[]string `toml:"whitelist-l2-token-list"`

// UpperMinGasLimit is the upper limit of the minimum gas limit of the L2StandardBridgeBot contract.
//
// **IMPORTANT: If this value is unset (by default), the L2StandardBridgeBot contract doesn't limit the minimum gas limit.**
UpperMinGasLimit *uint32 `toml:"upper-min-gas-limit"`

// UpperExtraDataSize is the upper limit of the extra data size of the L2StandardBridgeBot contract.
//
// **IMPORTANT: If this value is unset (by default), the L2StandardBridgeBot contract doesn't limit the extra data size.**
UpperExtraDataSize *uint32 `toml:"upper-extra-data-size"`