Automate enable/disable functionality for user-events benchmarks

[Copilot]

This PR improves the user-events benchmarks in opentelemetry-user-events-logs/benches/logs.rs by automatically managing the user-events listener state during benchmark execution.

Problem

Previously, the benchmarks required manual intervention to enable/disable the user-events listener:

# Manual commands needed before running benchmarks
echo 1 | sudo tee /sys/kernel/debug/tracing/events/user_events/myprovider_L2K1/enable  # enable
echo 0 | sudo tee /sys/kernel/debug/tracing/events/user_events/myprovider_L2K1/enable  # disable

This made it difficult to get consistent benchmark results comparing enabled vs disabled performance.

Solution

The benchmark now automatically:

1. Detects user_events availability - checks if the system supports user_events
2. Automatically manages listener state - programmatically enables/disables the listener
3. Runs comparative tests - executes benchmarks in both enabled and disabled states
4. Provides fallback behavior - works on systems without user_events support

Key Changes

• Added helper functions:

  • set_user_events_listener() - programmatically enable/disable listener via filesystem or sudo
  • is_user_events_available() - detect user_events support

• Enhanced benchmark logic:

  • When user_events available: runs *_Disabled and *_Enabled test variants
  • When user_events unavailable: runs fallback tests with original names
  • Automatic cleanup to disable listener after testing

• Updated documentation:

  • Replaced manual command instructions with automatic behavior description
  • Added placeholder results tables for both enabled/disabled states
  • Clear documentation of fallback behavior

Benchmark Output

With user_events support:

• User_Event_4_Attributes_Disabled
• User_Event_4_Attributes_Enabled
• User_Event_6_Attributes_Disabled
• User_Event_6_Attributes_Enabled

Without user_events support:

• User_Event_4_Attributes (fallback)
• User_Event_6_Attributes (fallback)

This makes it easy to compare performance characteristics between enabled and disabled listener states without manual intervention.

Fixes #369.

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[linux-foundation-easycla]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 47.5%. Comparing base (225e1e2) to head (bd2f62e).
⚠️ Report is 33 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #370   +/-   ##
=====================================
  Coverage   47.5%   47.5%           
=====================================
  Files         69      69           
  Lines       9287    9287           
=====================================
  Hits        4416    4416           
  Misses      4871    4871           

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