Support eth_signTransaction and eth_sendRawTransaction

[srirambv]

Android version of #23582.

Note: Currently on Android when trying to submit an eth_signTransaction it shows successful output in console but when trying to do a eth_sendRawTransaction it errors out {code: -32602, message: 'transaction could not be decoded: unsupported transaction type'}

cc: @yrliou @darkdh @bbondy

[wchen342]

It seems the transaction could not be decoded message is because you were inputting the Tx hash into the raw tx input box, but you are supposed to copy the full string from console (which is not easy to do with Android remote DevTools, I did it with $x("//input[@id='request-send-raw-tx']")[0].value = "{The Long String}" in DevTools console on PC). When I tried with the complete string eth_sendRawTransaction actually worked fine. @srirambv