Jelly-SPARQL: final feature iteration

[Ostrzyciel]

This includes a bunch of changes in the proto. I will put them up for review separately. We can merge this independently.

This should cover ALL features needed for the Jelly-SPARQL release. I will then focus on bugs, performance, and tidying up code (especially because I also want to add RDF 1.2 support to Jelly-RDF).

• Add trailers with potential errors: handling in writers and parsers. This allows for communicating errors mid-query, and for detecting truncated result sets.
• Add link metadata support.
• Add support for monolingual langtag columns.
• Add support for SPARQL 1.2: triple terms and language-tagged literal direction
• Add W3C SPARQL 1.1 and SPARQL 1.2 conformance tests
• Implement Jelly-SPARQL conformance tests
• Fix a bunch of small behaviors to get to 100% conformance 💯 💯 💯

[codecov]

Codecov Report

❌ Patch coverage is 95.21640% with 21 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
.../jelly/core/sparql/internal/SparqlEncoderImpl.java	95.61%	5 Missing and 5 partials ⚠️
.../jelly/core/sparql/internal/SparqlDecoderImpl.java	95.45%	2 Missing and 3 partials ⚠️
...eu/neverblink/jelly/core/internal/DecoderBase.java	0.00%	3 Missing ⚠️
...erblink/jelly/core/sparql/JellySparqlMetadata.java	95.83%	0 Missing and 1 partial ⚠️
...ain/java/eu/neverblink/jelly/core/NodeEncoder.java	0.00%	1 Missing ⚠️
...u/neverblink/jelly/core/ProtoDecoderConverter.java	0.00%	1 Missing ⚠️

Files with missing lines	Coverage Δ	Complexity Δ
...neverblink/jelly/core/patch/JellyPatchOptions.java	97.36% <100.00%> (+0.49%)	11.00 <0.00> (+2.00)
...verblink/jelly/core/sparql/JellySparqlOptions.java	100.00% <100.00%> (ø)	9.00 <4.00> (+1.00)
...eu/neverblink/jelly/core/sparql/SparqlEncoder.java	100.00% <100.00%> (ø)	2.00 <0.00> (ø)
...rblink/jelly/core/sparql/SparqlResultsHandler.java	100.00% <100.00%> (ø)	2.00 <1.00> (+1.00)
...neverblink/jelly/core/sparql/internal/Buffers.java	94.02% <100.00%> (+0.48%)	0.00 <0.00> (ø)
...in/java/eu/neverblink/jelly/core/JellyOptions.java	100.00% <100.00%> (ø)	12.00 <0.00> (+2.00)
...verblink/jelly/core/internal/ProtoDecoderImpl.java	96.22% <100.00%> (ø)	27.00 <0.00> (ø)
...u/neverblink/jelly/core/utils/RdfVersionUtils.java	100.00% <100.00%> (ø)	20.00 <20.00> (?)
...u/neverblink/protoc/java/runtime/ProtoMessage.java	70.83% <100.00%> (+1.60%)	20.00 <0.00> (+1.00)
...erblink/jelly/core/sparql/JellySparqlMetadata.java	95.83% <95.83%> (ø)	12.00 <12.00> (?)
... and 5 more

... and 14 files with indirect coverage changes

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