chore: 🎸 add tx overrides to tsml

[JustinFeng]

Expect to handle transaction overrides arguments like this

<ts:transaction>
    <ethereum:transaction as="uint" contract="SmartCatScore" function="feedCat">
	<ts:data>
		<ts:uint256 ref="tokenId"/>
	</ts:data>
	<ethereum:overrides>
                <ts:uint256 name="gasLimit">200000</ts:uint256>
	</ethereum:overrides>
    </ethereum:transaction>
</ts:transaction>

Note: this PR is in draft status, it aims to collect early feedback regarding whether this is moving to the right direction, cheers