[DOC] Release notes for Pyroscope 1.3

[knylander-grafana]

Create release notes for the next release.

Tasks:

• Create a summary of the new features and major improvements
• Verify docs are available for ther updated features and link to those docs from the release notes
• Update the "Upgrade to Pyroscope" page with any breaking changes or caveats for the next release

[knylander-grafana]

Major new features:

• Downsampling and compactor performance improvements are new

Draft content from Ryan:

New Features

• Enhanced symbol compaction process: Improved performance and storage efficiency with the new symbol compaction process (#2864).
• Introduced function selector in pprof query: More precise profiling with the addition of a function selector (#2878).
• Support for time-based downsampling during compaction: Optimized data processing with time-based strategies (#2880).
• Added tracing integrations to compaction: Better observability in the compaction process (#2876).
• Added language mapping for Grafana agent in Java: Expanded profiling capabilities (#2866).

Improvements and Updates

• Updated Alpine and Golang versions: Enhanced security and performance with the latest versions of Alpine (3.18.5) and Golang (1.21.5) (#2901, #2902).
• Injected JFR labels into pprof: Enriched profiling data for better insights (#2868).
• Streamlined Makefile and go.mod: Better build process with updated Makefile and tidied go.mod (#2900).
• Updated agent configuration in Helm: More flexible deployments in Kubernetes environments (#2879).
• Refactored ebpf installation documentation: Improved clarity and usability in ebpf documentation (#2849).
• Upgraded connect-go, protobuf, and buf: Improved system interoperability (#2909).
• Enhanced compaction shutdown process: Improved system stability during shutdowns (#2903).
• Implemented profilecli compact command: Efficient data management with the new command (#2869).

Fixes

• Fixed panic in compaction benchmark: Addressed issues causing system instability (#2918).
• Resolved block cleanup process issues: Ensured system integrity and stability (#2916).
• Fixed pprof profile builder panics: Enhanced system stability (#2917).
• Corrected profile types call handling: Better data management without bucket store (#2910).
• Removed delta reserved labels from storage: Optimized the storage system (#2920).
• Increased parquet read buffer size: Improved data processing efficiency (#2924).

Documentation Improvements

• Enhanced memory overhead documentation: Deeper insights into system performance (#2895).
• Updated NodeJS documentation: Fixed Markdown link issues for better clarity (#2890).
• Expanded java.md documentation: Comprehensive Java profiling guidance (#2904).
• Removed dependency on Grafana agent: Streamlined Pyroscope architecture (#2913).
• Updated various sections: Intro, analyze, sampling, and SDK pages now offer clearer and more detailed information (#2855, #2844, #2854, #2851, #2861).
• Launched a 1-minute YouTube short on ebpf: Providing a quick and informative overview of ebpf (#2893).