Error Tracking: Remove unused collector utilities

What does this MR do and why?

Error Tracking with the Postgres backend was disabled in #353639 (closed) (%14.9).

This MR removes parts of unused backend and contributes to #414933.

Follow-up of !123139 (merged)

MR navigation

• Error Tracking: Remove ingestion API (!123139 - merged)
• Error Tracking: Remove unused collector utilities
• Error Tracking: Remove unused ActiveRecordStrategy (!123651 - merged)

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.