[Feature Request]: Implement JsonIO.read() / readRows() for the Java SDK

### What would you like to happen?

## Motivation

The Java `JsonIO` connector (`sdks/java/io/json/.../JsonIO.java`) currently supports only writing with`JsonIO.write()` and `JsonIO.writeRows()`. There is no read path. The connector's own class Javadoc acknowledges this gap:

> "Reading from JSON files is not yet implemented in Java. Please see
> https://github.com/apache/beam/issues/24552."

That linked issue (#24552) is actually titled "Implement CsvIO.Read" and is closed as *not planned*, CsvIO.Read was subsequently implemented under a different path, so there is currently **no live tracking issue** for JSON reading, and the Javadoc reference is stale. This issue is intended to be that tracking issue.

## Proposal

Add a read/parse surface to `JsonIO` symmetric to the existing write surface
and mirroring the pattern `CsvIO` already established:

```java
JsonIO.parse(Class klass) // JSON records -> user type T
JsonIO.parseRows(Schema schema) // JSON records -> Row
```
modeled on CsvIO.parse(Class, CSVFormat) (CsvIO.java:419) and CsvIO.parseRows(Schema, CSVFormat) (CsvIO.java:497), including their CsvIOParse result-and-error-handling pattern.

**Why this is tractable**

The core JSON→Row conversion already exists and is reusable:

- JsonUtils.getJsonStringToRowFunction(Schema)
(sdks/java/core/.../schemas/utils/JsonUtils.java:104)
- JsonUtils.getJsonBytesToRowFunction(Schema) (line 93)
- JsonUtils.beamSchemaFromJsonSchema(String) (line 201)

The work is primarily wiring these into a read PTransform over FileIO.match() + line reading, following the CsvIO parse structure not new parsing logic.

**Testing plan**

- Unit tests mirroring CsvIO parse tests: schema validation, type conversion to both Row and custom user classes, error/failure routing.
- Round-trip test: write JSON via JsonIO.write(), read it back via JsonIO.parseRows(), assert equality.
- No new dependencies- JSON schema/parse machinery is already in sdks/java/core.

### Issue Priority

Priority: 2 (default / most feature requests should be filed as P2)

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