Previous commit was a hack which *always* batched where possible, this
is a more sophisticated opt-in varaint, with a timeout sanity check.
Final performance for cleaning up 1M pays/forwards/invoices:
```
$ time l1-cli autoclean-once succeededpays 1
{
"autoclean": {
"succeededpays": {
"cleaned": 1000000,
"uncleaned": 26895
}
}
}
real 6m9.828s
user 0m0.003s
sys 0m0.001s
$ time l2-cli autoclean-once succeededforwards 1
{
"autoclean": {
"succeededforwards": {
"cleaned": 1000000,
"uncleaned": 40
}
}
}
real 3m20.789s
user 0m0.004s
sys 0m0.001s
$ time l3-cli autoclean-once paidinvoices 1
{
"autoclean": {
"paidinvoices": {
"cleaned": 1000000,
"uncleaned": 0
}
}
}
real 6m47.941s
user 0m0.001s
sys 0m0.000s
```
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Added: JSON-RPC: `batching` command to allow database transactions to cross multiple back-to-back JSON commands.
Rusty Russell