feat(sdk): Make it easier to get transaction estimates

Description:

Instead of adding all the transaction fields, have serialize only add the fields we need.

This lets developers use the code pattern:

```js
const txReq = await greeter.populateTransaction.setGreeting(greeting)
const tx = await signer.populateTransaction(txReq)
provider.estimateL1Gas(tx)
```

Instead of the more error prone:

```js
const txReq = await greeter.populateTransaction.setGreeting(greeting)
const tx = await signer.populateTransaction(txReq)
delete tx.from
delete tx.chainId
provider.estimateL1Gas(tx)
```

packages/sdk/src/l2-provider.ts

@@ -48,7 +48,11 @@ export const estimateL1Gas = async (
   const gpo = connectGasPriceOracle(l2Provider)
   return gpo.getL1GasUsed(
     serialize({
-      ...tx,
+      data: tx.data,
+      to: tx.to,
+      gasPrice: tx.gasPrice,
+      type: tx.type,
+      gasLimit: tx.gasLimit,
       nonce: toNumber(tx.nonce as NumberLike),
     })
   )
@@ -68,7 +72,11 @@ export const estimateL1GasCost = async (
   const gpo = connectGasPriceOracle(l2Provider)
   return gpo.getL1Fee(
     serialize({
-      ...tx,
+      data: tx.data,
+      to: tx.to,
+      gasPrice: tx.gasPrice,
+      type: tx.type,
+      gasLimit: tx.gasLimit,
       nonce: toNumber(tx.nonce as NumberLike),
     })
   )