Collect system info in consecutive tests mode with per-test label association

[Copilot]

System resource snapshots (system_info) were only collected during parallel execution via run_on_wait. In consecutive mode, no system info was recorded. Additionally, there was no way to associate a system snapshot with the specific test that was running at the time.

Schema (ddl/create.sql)

• Added test_label VARCHAR(255) DEFAULT '' to system_info table — links each snapshot to the executing test
• Updated system_info_view to expose test_label

Driver (bin/driver.pl)

• Updated SQL_SYS_INFO to include test_label
• Added memory/CPU collection before each command in consecutive mode, tagging each snapshot with label4run:

  my @sysdata = ($mem->{USED}, ..., $mem->{PMEM_USED}, $pcpu, $label4run);
  &save2db($sth_sysinfo, $host_id, @sysdata);

• Parallel mode passes '' as test_label (schema compatibility; individual label attribution isn't meaningful there)

Test data (ddl/insert.sql)

• Updated system_info fixture inserts to include test_label values

• Fixes Collect system information in consecutive tests mode #14