Add support for Privy embedded wallets with delegation

[CarsonRoscoe]

This PR is a continuation of #583

Description

This PR adds support for Privy's embedded wallets with delegation to AgentKit. It introduces a new wallet provider, PrivyEvmEmbeddedWalletProvider, that allows AgentKit to use wallets which have been delegated transaction signing authority through Privy's embedded wallet system. This enables autonomous agents to perform onchain actions on behalf of users.

The implementation:

• Creates a new PrivyEvmEmbeddedWalletProvider class that extends EvmWalletProvider
• Updates the PrivyWalletProvider factory to support embedded wallets via a new walletType option
• Adds comprehensive test coverage for the new provider
• Updates documentation on how to use the embedded wallet provider

Currently our UI uses Privy's embedded wallet for delegation to agents, but Coinbase's agent kit only supports Privy's server wallet. This change makes the two systems compatible, allowing agents to properly execute transactions with delegated embedded wallets.

Tests

See original authors tests here: #583

Below are my own tests in addition to the above:

Prompt: Do a native transfer, using the value 0.00001 ETH, and transfer to 0x13f2344Df67CB87f5f6C4809f396696c839e0A5A. Do not convert that number, pass in exactly 0.00001 sas the value

-------------------
Wallet Details:
- Provider: privy_evm_embedded_wallet_provider
- Address: 0xc342103DA49ed761C555f58fE336C8E7Ef2d587a
- Network:
  * Protocol Family: evm
  * Network ID: base-sepolia
  * Chain ID: 84532
- Native Balance: 199612217380681 WEI
-------------------

-------------------
Transferred 0.00001 ETH to 0x13f2344Df67CB87f5f6C4809f396696c839e0A5A
Transaction hash: 0x8da3cd3a39148e63da57c211d240bb2e39925177b147fb5d0e0cf92dd0256e11
-------------------
Successfully transferred **0.00001 ETH** to **0x13f2344Df67CB87f5f6C4809f396696c839e0A5A**. 

Transaction hash: **0x8da3cd3a39148e63da57c211d240bb2e39925177b147fb5d0e0cf92dd0256e11**.
-------------------

Prompt: faucet USDC
The faucet is only available on the 'base-sepolia' network for the assets 'eth' or 'usdc'. Since we are currently on the 'base-sepolia' network, I can request USDC for you.

Let's proceed with requesting USDC from the faucet.
-------------------
Received usdc from the faucet. Transaction: https://sepolia.basescan.org/tx/0xda803c3c2c5e906fd7b8344713149adc34bdea2f854cf0922058dcd185e7eb46
-------------------
Successfully received **USDC** from the faucet. You can view the transaction details [here](https://sepolia.basescan.org/tx/0xda803c3c2c5e906fd7b8344713149adc34bdea2f854cf0922058dcd185e7eb46).
-------------------

Prompt: Send 0.5 USDC (500000 units, contract address 0x036CbD53842c5426634e7929541eC2318f3dCF7e) to 0x13f2344Df67CB87f5f6C4809f396696c839e0A5A

-------------------
Transferred 500000 of 0x036CbD53842c5426634e7929541eC2318f3dCF7e to 0x13f2344Df67CB87f5f6C4809f396696c839e0A5A.
Transaction hash for the transfer: 0xd7c6e98efc2a85eaf583be31adbd47453ccb62481c09d912a823efd472175883
-------------------
Successfully transferred **0.5 USDC** (500,000 units) to **0x13f2344Df67CB87f5f6C4809f396696c839e0A5A**.

Transaction hash: **0xd7c6e98efc2a85eaf583be31adbd47453ccb62481c09d912a823efd472175883**.

Checklist

A couple of things to include in your PR for completeness:

• Added documentation to all relevant README.md files
• Added a changelog entry

[cb-heimdall]

✅ Heimdall Review Status

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[0xRAG]

LGTM