lightningd: treat JSON ids as direct tokens.

This avoids any confusion between primitive and string ids, and in
particular stops an issue with commando once it starts chaining ids,
that weird ids can be double-escaped and commando will not recognize
the response, leaving the client hanging.  It's the client's fault for
using a weird id, but it's still rude (and triggered by our tests!).

It also makes substituting the id in passthrough simpler, FTW.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

tests/test_misc.py

@@ -874,7 +874,7 @@ def test_cli(node_factory):
     assert 'help [command]\n    List available commands, or give verbose help on one {command}' in out
 
     # Check JSON id is as expected
-    l1.daemon.wait_for_log(r"jsonrpc#[0-9]*: cli:help#[0-9]*\[IN\]")
+    l1.daemon.wait_for_log(r'jsonrpc#[0-9]*: "cli:help#[0-9]*"\[IN\]')
 
     # Test JSON output.
     out = subprocess.check_output(['cli/lightning-cli',