feat: Display ftyp minor_version as number or 4CC

[y-guyon]

ISO/IEC 23008-12:2025/DAmd 2 "Information technology — High efficiency coding and media delivery in heterogeneous environments — Part 12: Image File Format — Amendment 2: Low-overhead image file format" reuses the minor_version field of the FileTypeBox to store a brand in a similar manner as major_brand and compatible_brands[].

This is made possible by ISO/IEC FDIS 14496-12/DAmd 1 "Information technology — Coding of audio-visual objects — Part 12: ISO base media file format — Amendment 1: Tools for enhanced CMAF and DASH integration" which allows for arbitrary usage of minor_version in derived specifications depending on the major brand.

This PR shows the minor_version field as a number (current behavior) unless it is an alphanumeric 4CC (new behavior). Most existing files (at least HEIF-based ones) should have minor_version set to 0, and it is expected that files setting minor_version to another value than 0 will be using it to store a brand.