invoice+rpc: add exit hop InvoiceAcceptor sub-systems and RPC calls#8669

ffranr wants to merge 35 commits intolightningnetwork:custom-channels-integrationlightningnetwork/lnd:custom-channels-integrationfrom

ffranr:8616-invoice+rpc-add-exit-hop-invoiceacceptor-sub-systems-and-rpc-callsffranr/lnd:8616-invoice+rpc-add-exit-hop-invoiceacceptor-sub-systems-and-rpc-callsCopy head branch name to clipboard