Bug "(event_name cpu-clock)"

Running
```
./magic-trace run glxinfo64 -- -B
```
I get
```
Intel PT support not found. magic-trace will continue and use sampling instead.
Warning: [-callgraph-mode] is defaulting to [Dwarf] which may have high overhead and decoding time. For more info: https://magic-trace.org/w/b
[ Snapshot taken. ]
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.127 MB /tmp/magic_trace.tmp.72c3de/perf.data (12 samples) ]
[ Finished recording. ]
[ Decoding, this takes a while... ]
Warning: Debug info is unavailable, so filenames and line numbers will not be available in the trace.
See https://github.com/janestreet/magic-trace/wiki/Compiling-code-for-maximum-compatibility-with-magic-trace for more info.
(monitor.ml.Error
("BUG: exception raised while parsing perf output. Please report this to https://github.com/janestreet/magic-trace/issues/"
(exn
("Unexpected event type when parsing perf output" (event_name cpu-clock)))
(perf_output
(" 5488/5488 1539.632720267: 100000 cpu-clock:uH: "
"\t 7fb9b09ba370 [unknown] (/usr/lib64/libexpat.so.1.8.10)"
"\t 7fb9b09bd38c [unknown] (/usr/lib64/libexpat.so.1.8.10)"
"\t 7fb9b09bd4e3 [unknown] (/usr/lib64/libexpat.so.1.8.10)"
"\t 7fb9b09beb7c [unknown] (/usr/lib64/libexpat.so.1.8.10)"
"\t 7fb9b09c332c [unknown] (/usr/lib64/libexpat.so.1.8.10)"
"\t 7fb9b09c46c5 [unknown] (/usr/lib64/libexpat.so.1.8.10)"
"\t 7fb9b09c6b2f XML_ParseBuffer+0x7f (/usr/lib64/libexpat.so.1.8.10)"
"\t 7fb9b0abca85 [unknown] (/usr/lib64/libGLX_mesa.so.0.0.0)"
"\t 7fb9b0abe63a [unknown] (/usr/lib64/libGLX_mesa.so.0.0.0)"
"\t 7fb9b0ab870a [unknown] (/usr/lib64/libGLX_mesa.so.0.0.0)"
"\t 7fb9b0aaceae [unknown] (/usr/lib64/libGLX_mesa.so.0.0.0)"
"\t 7fb9b0a9e6e8 [unknown] (/usr/lib64/libGLX_mesa.so.0.0.0)"
"\t 7fb9b0a9a4c8 [unknown] (/usr/lib64/libGLX_mesa.so.0.0.0)"
"\t 56458a6b7894 [unknown] ([unknown])"
"\t 7fb9b0c35149 __libc_start_call_main+0x79 (/usr/lib64/libc.so.6)"
"\t 7fb9b0c3520a __libc_start_main@@GLIBC_2.34+0x8a (/usr/lib64/libc.so.6)"
"\t 56458a6b8354 [unknown] ([unknown])")))
("Raised at Base__Error.raise in file \"src/error.ml\" (inlined), line 9, characters 14-30"
"Called from Base__Error.raise_s in file \"src/error.ml\", line 10, characters 19-40"
"Called from Async_kernel__Pipe.map.(fun) in file \"src/pipe.ml\", line 1042, characters 65-70"
"Called from Async_kernel__Job_queue.run_jobs in file \"src/job_queue.ml\", line 167, characters 6-47"
"Caught by monitor Monitor.protect"))
```

This is on
```
uname -a
Linux fedora 6.5.9-300.fc39.x86_64 #1 SMP PREEMPT_DYNAMIC Wed Oct 25 21:39:20 UTC 2023 x86_64 GNU/Linux

perf --version
perf version 6.5.4

cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 141
model name : 11th Gen Intel(R) Core(TM) i7-11800H @ 2.30GHz
```
which is all Fedora Linux 39 (on VMware Workstation 17.5, running on Windows 11 Professional - which should not matter all that much for the problem I am trying to investigate)

So, this is a bit of a bleeding edge, I guess...

Reproduce the failure with `./magic-trace run glxinfo64 -- -B` and inspect the parser handling the `Unexpected event type when parsing perf output` error. Use the reported `cpu-clock` event and perf output as the case to investigate; done means this valid output no longer causes the trace run to fail.

Written by the indexing model from the issue text.