feat(eap): Sort trace item attributes by frequency

[volokluev]

Return attribute keys sorted by frequency (count) in descending order, with alphabetical ordering as a tiebreaker for attributes with the same frequency.

This change makes it easier for users to discover the most commonly used attributes in their traces by surfacing them first in the results.

Motivation

Previously, attributes were returned in alphabetical order only, which meant frequently-used, important attributes could be buried among less relevant ones. By sorting by frequency first, users can quickly identify which attributes are most prevalent in their data.

Changes

• Modified the ClickHouse query to group by attribute key and count occurrences
• Updated ORDER BY clause to sort by count DESC, then attr_key ASC as a tiebreaker
• Updated result processing to handle the additional count column
• Added two new tests to verify frequency-based sorting behavior:
  • test_sorted_by_frequency: Verifies alphabetical sorting when attributes have equal frequency
  • test_frequency_ordering_with_specific_attributes: Validates sorting with filtered results

Technical Details

The query now uses count() with GROUP BY attr_key instead of distinct(), which allows us to order by frequency. Non-stored attributes (like sentry.service) are assigned a very high count to ensure they appear first.

Refs EAP-432

🤖 Generated with Claude Code

[linear-code]

EAP-432 Support sorting by `count()` desc in TraceItemAttributeNamesRequest