feat: disable wallet buttons for accounts that cannot sign transactions

[k-g-j]

Description

This PR disables certain buttons in the WalletActions component when the selected account cannot sign transactions. This change improves the user experience by preventing attempts to perform actions that require transaction signing when the account cannot do so.

1. The reason for the change is to prevent users from attempting actions that their current account cannot perform.
2. The improvement is that Buy, Sell, Send, Swap, and Bridge buttons are now disabled when the selected account cannot sign transactions, providing clear visual feedback to the user about available actions.

Related issues

Fixes: https://github.com/MetaMask/accounts-planning/issues/570

Manual testing steps

1. Go to the SSK and create an account
2. Update the account using this JSON, replacing the address and ID fields with the new account information (this update step removes eth_signTransaction from the account's methods)

{
    "id": "your new account ID",
    "address": "you new account address",
    "options": {},
    "methods": [
        "personal_sign",
        "eth_sign",
        "eth_signTypedData_v1",
        "eth_signTypedData_v3",
        "eth_signTypedData_v4"
    ],
    "type": "eip155:eoa"
}

3. Switch to the account that cannot sign transactions if not already there
4. Verify that the Buy, Sell, Send, Swap, and Bridge buttons are visually disabled with a message
5. Attempt to tap on these buttons and confirm that no action is taken
6. Switch back to an account that can sign transactions
7. Verify that the buttons are now enabled and functional

Screenshots/Recordings

Before

[Insert screenshot of WalletActions before the change, with all buttons enabled]

After

[Insert screenshot of WalletActions after the change, with relevant buttons disabled for an account that can't sign transactions]

Pre-merge author checklist

• I've followed MetaMask Contributor Docs and MetaMask Mobile Coding Standards.
• I've completed the PR template to the best of my ability
• I've included tests if applicable
• I've documented my code using JSDoc format if applicable
• I've applied the right labels on the PR (see labeling guidelines). Not required for external contributors.

Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.

[github-actions]

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