test: strip directory from subtest name in summary

The integration tests are started with the absolute path of the test
unit as $0, so run_subtests() derives absolute paths for the subtests
and the summary prints them in full. Show just the script name, the
directory is the same for every entry and only adds noise.

Signed-off-by: Paul Meyer <katexochen0@gmail.com>

test/units/test-control.sh

@@ -84,6 +84,8 @@ _show_summary() {(
 _record_subtest_rc() {
     local subtest="${1:?}" rc="${2:?}"
 
+    subtest="${subtest##*/}"
+
     if [[ $rc -eq $_SUBTEST_SKIP_RC ]]; then
         echo "Subtest $subtest skipped"
         _SKIPPED_TESTS+=("$subtest")