missing sections around some output, and some other section issues

taking https://gitlab.freedesktop.org/mesa/mesa/-/jobs/67200692 for instance:

• lines 1772 to 1786, the mc mirror stuff should be in a section
• lines 1814 to 1818, log 'Start the containers pipeline' should be a section
• lines 1820 and 1821 should be inside the section at line 1819 "[41.17]: Execute the container_start hooks"
• lines 2290 to 2296 should be inside the section at line 2289 "[630.83]: Execute the container_end hooks", and that section should be closed by default
• lines 2297 to 2307, section "[630.84]: Execute the pipeline_end hooks" should be closed by default
• lines 2350 to 2354 could be in a section (but this one might be tricky as it's the last one and we don't want to risk having an unterminated section that would hide everything after)
• sections don't use unique identifiers, which means some section cannot be closed and clicking on some sections opens/closes other sections; take line 2289 for example, clicking on it doesn't affect its own section but the one below at line 2297 instead. The fix is to generate unique identifiers every time a section is created that only exists as long as that section exists.

(for context, all of this work on sections is in the interest of not showing "useless" information to the user in the normal case, and while still having it available for us to debug things when something's wrong)