feat: improve DataSchemaValue handling

[JKRhb]

This PR reworks both the internal handling of DataSchemaValues as well as the external API for passing in InteractionInputs. A potential InteractionInput is now more strongly typed and makes it possible to differentiate between DataSchemaValues and Streams more reliably. Due to these changes, the behavior of the library should now be more in line with the Scripting API specification which makes a clear distinction here.

However, this rework has some side effects: For instance, the new, stricter handling of DataSchemaValues disallows the use of CBOR objects that use non-string-based keys. Morever, it revealed some inconsistencies in the implementation of ContentCodecs as well as the validation logic in the value() method of the InteractionOutput interface. These aspects need to be improved in follow-up PRs.

Lastly, to improve code coverage and quality of the library, several additional tests are also included in this PR. Testing is another area that will be improved upon in upcoming PRs.

[codecov-commenter]

Codecov Report

Attention: 17 lines in your changes are missing coverage. Please review.

Comparison is base (e6610fe) 56.52% compared to head (2feb002) 59.61%.

Files	Patch %	Lines
lib/src/core/thing_discovery.dart	0.00%	10 Missing ⚠️
lib/src/core/consumed_thing.dart	0.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #86      +/-   ##
==========================================
+ Coverage   56.52%   59.61%   +3.09%     
==========================================
  Files          68       70       +2     
  Lines        2261     2387     +126     
==========================================
+ Hits         1278     1423     +145     
+ Misses        983      964      -19     

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