[feature]: Add Flag to BumpFee RPC and CLI to prevent batching

[starius]

Is your feature request related to a problem? Please describe.

When using the BumpFee RPC, I calculate the feerate based on the parent transaction's feerate and the desired effective feerate for a group of two transactions. Currently, the batcher may combine my input with another input in a batch CPFP (resulting in a 2:1 transaction), making it impossible to achieve the intended effective feerate.

Describe the solution you'd like

I propose adding an additional flag to BumpFee that forces the sweeper to assign the input to an exclusive group, ensuring it produces only a 1:1 child transaction (no batching).

I noticed that the sweeper already has an internal field called ExclusiveGroup. Would it be worth making this field public?

Describe alternatives you've considered

• If #5432 is implemented, I could use it to specify the desired effective feerate.
• Alternatively, I could perform CPFP manually instead of using the BumpFee RPC.

[yyforyongyu]

I think you can already do that by specifying a unique deadline, plus budget, then this would be managed by the sweeper,

&walletrpc.BumpFeeRequest{
	Outpoint: op,
	Immediate:  true,
	Budget: xxx,
	DeadlineDelta: xxx
}

calculate the feerate based on the parent transaction's feerate and the desired effective feerate for a group of two transactions.

Based on the description here I think you want to bypass the sweeper and manage the feerate manually - in that case we might as well add a new RPC that does one thing - create the tx with the desired feerate and publish it. There's no need to let it be managed by the sweeper since there's no aggregation or fee bumping involved.