Coswid human-readable serialization

Implement serialization for CoSWID structures that uses string field
names for human-readable formats and integer keys otherwise[*].

To support this, a number of changes have been made to core structures:

- Remove HashEntry, using Digest in its place
- Add additional conversion for ExtenstionValue from  native Rust types.
- Implement Role enum, and ermove generic Role from core that is no
  longer used.
- Implement human-readable serialization for TextOrBytesSized.
- Add From<i128> conversion for Label.
- Implement Add and Display for OneOreMore.
- Implement AttributeMap for global attributes (these can appear
  alongside extensions in CoSWID structures).
- Fix VersionScheme::Semver serialization value.

[*]: Unlike other CoRIM structures, CoSWID structures may contain string
entries for global attributes in non-human-readable encodings.

Signed-off-by: setrofim <[email protected]>

Author: setrofim