[Feature] Easier way to sign transactions with an external wallet + existing provider

### Component

provider, pubsub

### Describe the feature you would like

## Problem

I’m trying to interact with a contract bound via Alloy, where the provider is configured with the recommended fillers (so I can omit nonce, gas, fee fields etc.).

However, when I want to sign a transaction with a different wallet (not the one bound to the provider), I run into problems:

```
let tx = my_smart_contract
.call_function(/* args */)
.into_transaction_request()
.nonce(
my_smart_contract
.provider()
.get_transaction_count(from_account.address().to_alloy())
.await? + 1,
)
.with_gas_limit(21_000)
.with_max_priority_fee_per_gas(1_000_000_000)
.with_max_fee_per_gas(20_000_000_000)
.build(&wallet);

my_smart_contract
.provider()
.send_raw_transaction(&tx.encoded_2718())
.await?;
```

This works, but only if I manually set nonce/fees each time.
I’d like to avoid hardcoding values and refetching the nonce manually.
If those fields are not set, I get a `missing ["nonce", "gas_limit", "max_fee_per_gas", "max_priority_fee_per_gas"] fields` error.

I tried wrapping the provider with a wallet filler:
```
let provider_with_wallet =
FillProvider::new(my_smart_contract.provider().clone(), WalletFiller::new(wallet.clone())).erased();

let my_smart_contract = MyContract::Instance::new(*zeroex.address(), provider_with_wallet);

let response = my_smart_contract
.call_function(/* args */)
.send()
.await?;
```
But this fails with:
```
local usage error: missing properties: [("Wallet", ["nonce", "gas_limit", "max_fee_per_gas", "max_priority_fee_per_gas"])]
```
It seems like the recommended fillers from the original provider are not being applied once I switch to `FillProvider`.

## Expected

There should be a straightforward way to:
- Reuse the provider’s fillers (nonce, gas, fees, etc.)
- Swap in a different signing wallet
- Call `.send()` directly on contract bindings without manually specifying tx fields

### Additional context

_No response_