Speed up JSON schema inference by ~2.8x

[Rafferty97]

Which issue does this PR close?

This PR fixes #9484, and also sets the groundwork for implementing #9482. It also delivers an approximate 2.8x speed to JSON schema inference.

I have refactored the code that infers the schema of JSON sources, specifically:

• Simplify the type inference logic, removing special cases
• Schema inference now consumes TapeDecoder, eliminating the need to materialise rows into serde_json::Values first
• Use arena allocation for efficiency
• Remove scalar-to-array coersion, as the actual JSON reader doesn't support it
• Move ValueIter into its own module

Rationale for this change

While working on #9482, I saw a need and opportunity to refactor the schema inference code for JSON schemas. I also discovered the bug detailed in #9484.

These changes not only make the code more readible and predictable by eliminating a lot of special case handling, but make it trivial to create a new inference function for "single field" JSON reading.

They have also provided a significant performance boost to the schema inference functions. I added a simple benchmark for infer_json_schema, which yielded the following results on my machine, reflecting an approx. 2.8x speed up:

Before changes:
infer_json_schema/1000 time: [1.4443 ms 1.4616 ms 1.4793 ms]
thrpt: [85.336 MiB/s 86.366 MiB/s 87.401 MiB/s]

After changes:
infer_json_schema/1000 time: [517.79 µs 519.10 µs 520.54 µs]
thrpt: [242.51 MiB/s 243.18 MiB/s 243.80 MiB/s]
change:
time: [−64.919% −64.485% −64.043%] (p = 0.00 < 0.05)
thrpt: [+178.11% +181.57% +185.06%]

What changes are included in this PR?

At a glance:

• An overhaul of arrow-json/src/reader/schema.rs
• Removed mixed_arrays.json as it's no longer valid, and replaced mixed_arrays.json.gz with arrays.json.gz
• Added a dependency on Bumpalo for arena allocation

Because this is a somewhat sizeable PR, I've done my best to break into a logical sequence of commits to hopefully assist with the review.

Are these changes tested?

Yes, the changes pass all existing unit tests - except for one intentionally removed due to the change in behaviour related to #9484 (removing scalar-to-array promotion).

I have also added an additional benchmark for the schema inference performance.

Are there any user-facing changes?

There are no API changes, except for the addition of the record_count method on ValueIter.

However, the error messages returned by infer_json_schema and its cousins will significantly change, with most of them condensed to a single "Expected {expected}, found {got}" template.

Finally, some files that used to generate a valid schema will now return errors. However, this is desirable because those files would have failed to be read by the actual JSON reader anyway - due to the lack of support for scalar-to-array promotion in the JSON reader. (See #9484)