[clickhouse] upload logs on test failure (#4796)

Part of trying to figure out #4779 -- we now create ClickHouse logs in a
well-named directory which gets not-cleaned up (and therefore uploaded) at the end.

Tested this by introducing a failure in a test, and then seeing the following files in `/tmp`:

```
% find test_all-c4d6fc05c1fc48de-test_local_users.3329283.1-clickhouse-I4Af08 
test_all-c4d6fc05c1fc48de-test_local_users.3329283.1-clickhouse-I4Af08
test_all-c4d6fc05c1fc48de-test_local_users.3329283.1-clickhouse-I4Af08/log
test_all-c4d6fc05c1fc48de-test_local_users.3329283.1-clickhouse-I4Af08/clickhouse-server.log
test_all-c4d6fc05c1fc48de-test_local_users.3329283.1-clickhouse-I4Af08/clickhouse-server.errlog
```

.github/buildomat/jobs/build-and-test-helios.sh

@@ -5,7 +5,7 @@
 #: target = "helios-2.0"
 #: rust_toolchain = "1.72.1"
 #: output_rules = [
-#:	"/var/tmp/omicron_tmp/*",
+#:	"%/var/tmp/omicron_tmp/*",
 #:	"!/var/tmp/omicron_tmp/crdb-base*",
 #:	"!/var/tmp/omicron_tmp/rustc*",
 #: ]

.github/buildomat/jobs/build-and-test-linux.sh

@@ -5,7 +5,7 @@
 #: target = "ubuntu-22.04"
 #: rust_toolchain = "1.72.1"
 #: output_rules = [
-#:	"/var/tmp/omicron_tmp/*",
+#:	"%/var/tmp/omicron_tmp/*",
 #:	"!/var/tmp/omicron_tmp/crdb-base*",
 #:	"!/var/tmp/omicron_tmp/rustc*",
 #: ]