Removal of `ci_build_trace_sections` application code

The table ci_build_trace_sections is currently at about 220 GB including indexes and growing. We don't have a retention strategy expiring data. We are already running into int4 overflow issues in #23924 (comment 220249448), but that is a separate issue.

The table currently grows at about 20 GB per month, including indexes.

The question here is: Can we expire (delete) data from ci_build_trace_sections at some point, e.g. after a year or so?

Chatops is currently the only consumer of that data AFAIS and per #23924 (comment 220342719). Apparently nobody is using this data at the moment.

Proposal

• Remove the use of parse_trace_sections! in BuildFinishedWorker
• Remove Ci::ExtractSectionsFromBuildTraceService
• Remove BuildTraceSection, BuildTraceSectionName and relative associations from project, build, etc.