Fixes #9558

Problem

Users reported (via the 2025 DevTools user survey) that clicking on tags
in the log event rows had no effect. There was no way to quickly filter
logs by a specific kind (e.g. stderr, flutter.error) by clicking on
the kind chip directly.

Solution

Made the kind chip in the log event rows clickable. When a user clicks
on a kind chip, it automatically applies a k:<kind> filter to the logs
table, showing only logs of that kind.

Changes

• Added an optional onKindTapped callback parameter to MetadataChips
  widget in metadata.dart
• Added an optional onTap callback to the base MetadataChip class
• Wrapped the chip with GestureDetector and MouseRegion when onTap
  is provided, showing a pointer cursor on hover to indicate it is clickable
• In _message_column.dart, passed an onKindTapped callback to
  MetadataChips that calls controller.setActiveFilter(query: 'k:$kind')
  when the kind chip is tapped

Behavior

• Clicking a kind chip → applies a k:<kind> filter to the logs table
• Clicking the row outside the tag → still selects the log as before
• No breaking changes → onKindTapped is optional, so existing
  usages of MetadataChips without the callback are unaffected

Testing

Manually tested by:

1. Running a Flutter app connected to DevTools
2. Opening the Logging screen
3. Clicking on a kind chip (e.g. flutter.frame) in a log row
4. Verified that the filter field updates to k:flutter.frame and only
   logs of that kind are shown
5. Verified that clicking outside the chip still selects the log row