feat(attributes): Add profile.start_timestamp attribute

[chargome]

Summary

• Add profile.start_timestamp (double) attribute for recording when a profile started
• Needed by the JS SDK (JS-2221) for span streaming, where scope contexts are converted to segment span attributes

[github-actions]

Semver Impact of This PR

🟡 Minor (new features)

📋 Changelog Preview

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New Features ✨

Attributes

• Add profile.start_timestamp attribute by chargome in #363

• Add calculated performance scores by loewenheim in #355
• Add rpc.response.status_code attribute by alexander-alderman-webb in #352
• Add rpc.method attribute by alexander-alderman-webb in #351
• Add app vitals start attributes by buenaflor in #353
• Add process.runtime.engine.* attributes by chargome in #347

Bug Fixes 🐛

• (attributes) Change several deprecation statuses to normalize to align with ingestion paths by constantinius in #350
• (create) Replace angle brackets in file names by loewenheim in #356

Internal Changes 🔧

• (gh) Remove myself from CODEOWNERS by lcian in #354
• Bump vulnerable js packages by chargome in #359

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