GH-51037: [C++] Replace RapidJSON with simdjson in JSON parser

[Reranko05]

Rationale for this change

This PR continues the simdjson migration by replacing the RapidJSON-based parsing implementation used by the JSON parser.

The existing parser uses RapidJSON's SAX/handler interface to parse JSON values and populate Arrow builders. This change replaces that implementation with simdjson's ondemand API while retaining the existing builder and type-inference logic.

Changes

• Replace the RapidJSON parser and handler interface with simdjson's ondemand API.
• Parse JSON documents using simdjson::ondemand::parser::iterate_many.
• Use ResolveSimdjsonResult() consistently when handling simdjson results.
• Preserve support for nested objects and arrays.
• Preserve explicit-schema and inferred-field behavior.
• Preserve unexpected-field handling for Error, Ignore, and InferType.
• Continue storing numeric values as raw JSON tokens.
• Trim trailing whitespace from numeric raw tokens to preserve existing behavior.
• Preserve JSON parse error propagation through Status::Invalid.
• Remove the parser's RapidJSON-specific dependencies.

Fixes: #51037

• GitHub Issue: [C++] Replace RapidJSON with simdjson in JSON parser #51037

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