Refactor commitment broadcast to always go through OnchainTxHandler

Refactor commitment broadcast to always go through OnchainTxHandler

Currently, our holder commitment broadcast only goes through the
`OnchainTxHandler` for anchor outputs channels because we can actually
bump the commitment transaction fees with it. For non-anchor outputs
channels, we would just broadcast once directly via the
`ChannelForceClosed` monitor update, without going through the
`OnchainTxHandler`.

As we add support for async signing, we need to be tolerable to signing
failures. A signing failure of our holder commitment will currently
panic, but once the panic is removed, we must be able to retry signing
once the signer is available. We can easily achieve this via the
existing `OnchainTxHandler::rebroadcast_pending_claims`, but this
requires that we first queue our holder commitment as a claim. This
commit ensures we do so everywhere we need to broadcast a holder
commitment transaction, regardless of the channel type.

Co-authored-by: Rachel Malonson <rachel@lightspark.com>