Add support for price bump when tx_type="auto"

[abicky]

Although the PR #59 introduced the price_bump parameter, it is currently applied only when the tx_type is set to "legacy" or "dynamic".
This PR adds support for the price_bump parameter when tx_type is "auto" as well.

I've confirmed that the CI in the cosmos-ethereum-ibc-lcp passes.
datachainlab/cosmos-ethereum-ibc-lcp#88

[Copilot]

Pull Request Overview

This PR adds support for the price_bump parameter when tx_type is set to "auto". Previously, price bumping was only supported for "legacy" and "dynamic" transaction types.

Key changes:

• Implemented price bump logic for TxTypeAuto in both legacy (pre-EIP-1559) and EIP-1559 modes
• Refactored gas price calculation into a reusable calculateGasPrice helper function
• Added ethereum.GasPricer1559 interface for EIP-1559 gas price suggestions
• Enhanced test coverage with new test functions for auto transaction type with price bumping

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
pkg/relay/ethereum/gas.go	Implements TxTypeAuto case with price bump support, refactors common gas price calculation logic into calculateGasPrice helper, changes default case to panic for unsupported tx types
pkg/relay/ethereum/gas_test.go	Adds test cases for price bumping with auto tx type (both legacy and EIP-1559 modes), updates MockChainClient to support EIP-1559 suggestions, fixes test comments and adds defensive copies for big.Int values
pkg/relay/ethereum/client.go	Extends IChainClient interface to include ethereum.GasPricer1559 for EIP-1559 gas price suggestions

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[Copilot]

Missing validation to check if the old transaction's gas values already exceed the suggestions. The TxTypeDynamic case includes this check (lines 58-62):

if oldTx != nil && oldTx.GasFeeCap != nil && oldTx.GasTipCap != nil {
    if oldTx.GasFeeCap.ToInt().Cmp(gasFeeCap) >= 0 && oldTx.GasTipCap.ToInt().Cmp(gasTipCap) >= 0 {
        return fmt.Errorf("old tx's gasFeeCap(%v) and gasTipCap(%v) are greater than or equal to suggestion(%v, %v)", ...)
    }
}

This validation should be added before line 118 to ensure that when both old tx values are already at or above the suggested values, an error is returned instead of attempting to use potentially stale values.

Suggested change

	}
	}
	if oldTx != nil && oldTx.GasFeeCap != nil && oldTx.GasTipCap != nil {
	if oldTx.GasFeeCap.ToInt().Cmp(gasFeeCap) >= 0 && oldTx.GasTipCap.ToInt().Cmp(gasTipCap) >= 0 {
	return fmt.Errorf("old tx's gasFeeCap(%v) and gasTipCap(%v) are greater than or equal to suggestion(%v, %v)", oldTx.GasFeeCap.ToInt(), oldTx.GasTipCap.ToInt(), gasFeeCap, gasTipCap)
	}
	}

[abicky]

I've added the validation in the commit 5c4ff80