feat: support reading of compressed trace files

[DavePearce]

Note

Adds transparent decompression for .gz/.bz2 trace files and updates readers to parse compressed inputs and line-based JSON batches.

• Utilities:
  • Add file.ReadAndUncompress to open and transparently decompress .gz/.bz2 files, returning stripped filename and raw data.
  • Introduce file.ReadInputFileAsLines (with .bz2 support) for efficient line-by-line reading.
• Trace IO:
  • Update cmd.ReadTraceFile to use ReadAndUncompress and resolve format based on the decompressed filename extension.
  • Update cmd.ReadBatchedTraceFile and tests (pkg/test/util/check_valid.go) to use ReadInputFileAsLines for batched JSON traces.
• Dependencies:
  • Import compress/gzip to support .gz decompression.

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