Bring JSON parser on par with circe-fs2

[satabin]

The goal of this PR is to have performances on par with circe-fs2, so that users can switch fearlessly to fs2-data (see circe/circe-fs2#425).
The existing two steps approach has a major drawback, that prevents this from happening: it builds intermediate Token, which are immediately consumed to build the AST using an instance of Builder.
This can be avoided for people coming from circe-fs2, by adding a new pipe ast.parse that directly transforms the input byte/char/string stream into the AST.

To achieve this, this PR takes inspiration from the Facade approach in jawn to model the ChunkAccumulator in the JSON parser. One such simple accumulator simply wraps the existing VectorBuilder[Token] and makes it possible to build the token stream. Another implementation (BuilderChunkAccumulator[Json]) directly builds the AST from the parser without instantiating any Token. In the future, it can even be extended to implement filtering at the source, without constructing the Tokens that are not selected. The abstraction is kept internal for now, so that we have more latitude to change the API and stabilize it.

• Implement the parser in terms of ChunkAccumulator
• Implement the simple TokenChunkAccumulator
• Implement the AST building BuilderChunkAccumulator
  • implement ast.parse
• Add sclafix rule to migrate from .through(tokens).through(ast.values) to .through(ast.parse)
• Add ast.parse documentation
• Add cookbook to migrate from circe-fs2

Using the new abstraction, here are the results of the benchmark.

Benchmark                                          Mode  Cnt     Score    Error  Units
JsonParserBenchmarks.parseCirceFs2                 avgt   10  5197.451 ± 18.083  us/op
JsonParserBenchmarks.parseJsonFs2DataParse         avgt   10  5259.336 ± 32.579  us/op
JsonParserBenchmarks.parseJsonFs2DataTokens        avgt   10  3531.900 ± 15.076  us/op
JsonParserBenchmarks.parseJsonFs2DataTokensValues  avgt   10  6091.062 ± 94.753  us/op
JsonParserBenchmarks.parseJsonJawn                 avgt   10  1945.402 ± 10.970  us/op
JsonValueBenchmarks.parseEscapedString             avgt   10     2.742 ±  0.021  us/op
JsonValueBenchmarks.parseSimpleString              avgt   10     2.588 ±  0.027  us/op

[satabin]

@ybasket this PR is ready to be reviewed!

[ybasket]

Nice work and sorry for the time it took me to review it!