Fix crash long logs

[Lagrang3]

Depends on #9138, because I am using the nice inline plugin test interface.

lightningd: fix crash after truncating long log messages

We were using vasprintf to generate the log line and then using free to
deallocate the string. However, in the case of a very long log line
a new pointer was created with tal_fmt and then tried to use free on it.

This was introduced in commit: 4d8f923a9a1468b8987dbb48e8fc988747f8c62f

```
free(): invalid pointer
lightningd: FATAL SIGNAL 6 (version v26.06-21-gebc5dc2)
0x563dab20be43 send_backtrace
        common/daemon.c:38
0x563dab20becd crashdump
        common/daemon.c:83
0x7f0cf0c96def ???
        ./signal/../sysdeps/unix/sysv/linux/x86_64/libc_sigaction.c:0
0x7f0cf0ceb95c __pthread_kill_implementation
        ./nptl/pthread_kill.c:44
0x7f0cf0c96cc1 __GI_raise
        ../sysdeps/posix/raise.c:26
0x7f0cf0c7f4ab __GI_abort
        ./stdlib/abort.c:77
0x7f0cf0c80290 __libc_message_impl
        ../sysdeps/posix/libc_fatal.c:134
0x7f0cf0cf5464 malloc_printerr
        ./malloc/malloc.c:5832
0x7f0cf0cfa41b _int_free_check
        ./malloc/malloc.c:4560
0x7f0cf0cfa41b _int_free
        ./malloc/malloc.c:4692
0x7f0cf0cfa41b __GI___libc_free
        ./malloc/malloc.c:3476
0x563dab19be60 logv
        lightningd/log.c:688
0x563dab19c0bc log_
        lightningd/log.c:728
0x563dab1c1047 plugin_log_handle
        lightningd/plugin.c:530
0x563dab1c5801 plugin_notification_handle
        lightningd/plugin.c:609
0x563dab1c5a9a plugin_read_json
        lightningd/plugin.c:753
0x563dab2388a5 next_plan
        ccan/ccan/io/io.c:60
0x563dab238c83 do_plan
        ccan/ccan/io/io.c:422
0x563dab238d3c io_ready
        ccan/ccan/io/io.c:439
0x563dab239e5b io_loop
        ccan/ccan/io/poll.c:470
0x563dab194399 io_loop_with_timers
        lightningd/io_loop_with_timers.c:22
0x563dab199c29 main
        lightningd/lightningd.c:1480
0x7f0cf0c80ca7 __libc_start_call_main
        ../sysdeps/nptl/libc_start_call_main.h:58
0x7f0cf0c80d64 __libc_start_main_impl
        ../csu/libc-start.c:360
0x563dab169020 ???
        _start+0x20:0
0xffffffffffffffff ???
        ???:0
```

[Lagrang3]

The discussion has moved to #9331