[Bug]: Can't switch rpc/network when tx has not been approved/rejected

**Describe the bug**

I can no longer switch rpc nodes before confirming/rejecting a transaction.

**Expected behavior**

This used to be possible, and now you have to cancel the tx, switch rpc nodes, then create the tx again. It's a substantial regression if you like to frequently swap between rpc networks - like mev protected, standard, or gas optimized rpc nodes.

**Steps to reproduce**

Create tx, attempt to swap between rpc nodes - selection is greyed out.

**Version**

11.7.3

**Build type**

None

**Browser**

Chrome

**Operating system**

Windows

Reproduce the issue by creating a transaction in MetaMask 11.7.3 and attempting to switch RPC nodes before approving or rejecting it. Trace the code behind the greyed-out RPC selection during a pending transaction, and consider the issue done when switching between RPC nodes works without cancelling and recreating the transaction.

Written by the indexing model from the issue text.