DA throttling

[dmarzzz]

https://discord.com/channels/1244729134312198194/1294422364473528331/1327389163045257249

Hey guy's wondering if any thought has been put into how to handle DA throttling within the block builder after the 1.9.5 batcher release. The op-batcher in this release will send a miner_setMaxDASize to the sequencing execution client to impose a throttle on tx size/max block size until the max pending queue bytes in the batcher is reduced below a configurable threshold. With an external block builder leveraging rollup-boost, the block builder will not be aware of the DA throttle imposed on the payloads, and will continue to build payloads at the standard gas limit accepted by the network. This opens up the chain to a spam attack.

I think there's two options here, wondering if anyone has a recommended solution:
Upstream changes to the batcher that multiplexes the miner_setMaxDASize call to the sequencer/(optional list of builder clients)
Place a Proxy service in front of the batcher to multiplex the miner_setMaxDASize call to the sequencer/(optional list of builder clients) e.g. proxyd, or similar service to rollup-boost

It seems like it might be advantageous to have this directly built into the batcher for chains running the rollup-boost stack, as to minimize complexity for the chain operator. It would be a fairly minor addition in the batcher.