CLN should inform user when/why sendrawtransaction fails

[btweenthebars]

Issue and Steps to Reproduce

I have some force closes that the closing transactions weren't broadcasted by bitcoind because "mempool min fee not met". The channels were hanging with AWAITING_UNILATERAL without having closing txs associated with the funding txs, by looking from the global blockchain explorers.

I had to turn on the debug log to grab the raw transactions and broadcast them manually over a blockchain explorer site.

there's no error messages even in the debug log. I had to try to broadcast them myself to see the issue.

I think, the bitcoind error message along with failed raw tx should be relayed to user either in the info log or better recorded in db so that it can be fetched somehow by "listpeers"

You may argue that such tx will be broadcasted eventually in this case when mempool is cheap enough but user might want to go with other options like using tx accelerator, or CPFP if possible. And what if bitcoind refuses with other reasons, user will be left frustrated having to shutdown and turn on debug log to find out. So I believe failing to sendrawtraction should be handle better.

getinfo output

"version": "v23.11.1-modded",

[cdecker]

The transactions are already tracked in the transactions table, and we could link to them from the listpeerchannels response. The TX broadcast not corresponding to an RPC command in many cases (except for successful calls to close from the PoV of the closing party), I wonder if it makes sense to bind this to an RPC method call too, as it would only be an ephemeral RPC response.