Add AggregateStats directive with ByteSize and TimeDuration parsing

[rahulmarripudi]

Summary

This PR introduces a new directive called AggregateStats that enables aggregation of data size and duration metrics from records.

Key Changes

• Implemented ByteSize.java and TimeDuration.java to parse human-readable units (e.g., "10KB", "5ms").
• Added AggregateStats.java directive to compute total size (in MB) and time (in seconds).
• Updated grammar files and parser visitors to support ByteSize and TimeDuration types.
• Included unit tests:
  • ByteSizeTests.java and TimeDurationTests.java
  • Testing Rig-based directive tests

Example Usage

aggregate-stats : data_size :duration total_size_mb total_time_sec

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