Add Perfetto trace import support with protobuf integration

[jlfwong]

Summary

• Adds support for importing Perfetto trace files into Speedscope
• Integrates Perfetto protobuf definitions for trace parsing
• Supports file extensions .perfetto-trace and .pftrace for automatic detection
• Includes a sample Perfetto trace file and a script to generate it
• Adds integration tests to verify Perfetto trace import functionality

Changes

Core Import Functionality

• Added perfetto.proto protobuf schema and generated JS/TS bindings
• Implemented importFromPerfettoTrace to parse Perfetto trace data
• Updated import index to detect and import Perfetto trace files by filename and content

Sample and Test

• Added a minimal sample Perfetto trace file under sample/profiles/perfetto/simple.perfetto-trace
• Created scripts/generate-perfetto-sample.js to generate the sample trace file
• Added perfetto-integration.test.ts with tests for importing Perfetto traces by filename and extension

Protobuf Integration

• Included generated protobuf JS and TypeScript declaration files for Perfetto trace format
• Ensures robust decoding and verification of Perfetto trace packets

Test plan

• Run integration tests to import sample Perfetto trace files
• Verify import does not crash and produces valid profile groups
• Confirm filename-based and extension-based detection works correctly

This PR enables Speedscope to handle Perfetto trace files, expanding its compatibility with popular tracing formats.

🌿 Generated by Terry

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📎 Task: https://www.terragonlabs.com/task/9a3333d4-48b1-4b5c-81e3-945192ea732f

Fixes #516