Clarify or Utilize `round` Parameter in `PendingStake` Method

Nobody has claimed this yet.

In the [PendingStake](https://arbiscan.io/address/0x35Bcf3c30594191d53231E4FF333E8A770453e40#readProxyContract#F19) method of the
[BondingManager](https://arbiscan.io/address/0x35Bcf3c30594191d53231E4FF333E8A770453e40#readProxyContract), the `round` parameter is currently unused:

[https://github.com/livepeer/protocol/blob/e8b6243c48d9db33852310d2aefedd5b1c77b8b6/contracts/bonding/BondingManager.sol#L935](https://github.com/livepeer/protocol/blob/e8b6243c48d9db33852310d2aefedd5b1c77b8b6/contracts/bonding/BondingManager.sol#L935)

To improve clarity and reduce potential confusion for integrators and developers, I propose one of the following actions:

1. **Update the method description and documentation** to explicitly state that the `round` parameter is currently unused, and clarify its intended purpose (if any future usage is planned).

2. **Upgrade the protocol to make use of the `round` parameter**, if there is an intended use case (e.g., allowing querying of stake at a specific round).

This change will help avoid misinterpretation and make the API more intuitive and self-explanatory for future development and integrations.

Start with the PendingStake method in contracts/bonding/BondingManager.sol around line 935 and review how its round parameter is exposed in the BondingManager interface and documentation. Determine whether the parameter has an intended use; done means either documenting that it is unused and explaining its purpose, or defining and implementing an agreed round-specific behavior.

Written by the indexing model from the issue text.