define a standard data format for metadata

[SadakazuNagao]

In the current version of ESSTRA, metadata embedded in binaries uses a custom YAML-based format.
This format was introduced as a temporary solution to demonstrate ESSTRA’s feasibility.

For future versions, we plan to define a standardized data format that addresses the following challenges:

• Reduce processing overhead caused by size bloat
• Improve interoperability with similar data types (e.g., SBOM)