[FLINK] Support Apache Pulsar as a datasource

### Description

Gluten Flink currently supports several Velox-backed datasources, such as Kafka, but Apache Pulsar is not supported yet.

This issue tracks adding Apache Pulsar as a datasource for Gluten Flink so Flink SQL streaming jobs can read from Pulsar topics through the Gluten/Velox execution path.

### Motivation

Apache Pulsar is widely used as a streaming messaging and storage system. Supporting Pulsar in Gluten Flink would allow users to run Flink SQL streaming workloads on Pulsar topics with Gluten/Velox acceleration.

### Example

```sql
CREATE TABLE pulsar_src (
id INT,
price INT,
name STRING
) WITH (
'connector' = 'pulsar',
'topics' = 'persistent://public/default/gluten-pulsar-smoke',
'service-url' = 'pulsar://127.0.0.1:6650',
'source.subscription-name' = 'gluten-pulsar-smoke-sub',
'source.subscription-type' = 'shared',
'source.start.message-id' = 'earliest',
'value.format' = 'json'
);

CREATE TABLE blackhole_sink (
id INT,
price INT
) WITH (
'connector' = 'blackhole'
);

INSERT INTO blackhole_sink
SELECT id, price FROM pulsar_src WHERE price > 10;
```

### Proposed Scope
Detect Flink Pulsar source transformations in Gluten Flink.
Convert Flink Pulsar table/source options into Velox Pulsar connector parameters.
Support common Pulsar source options:topic/topics
service URL
subscription name
subscription type, especially shared for parallel source readers
startup position such as earliest/latest
value format such as JSON

Register the Pulsar source factory in Gluten Flink.
Add unit tests for factory discovery and option mapping.
Validate the implementation with a local Pulsar standalone smoke test.
### Expected Behavior
A Flink SQL job reading from Pulsar should be able to run through Gluten/Velox.
With parallelism greater than 1, the source should support shared subscriptions so that multiple Pulsar consumers can read from the same topic without ConsumerBusy errors.
### Test Plan
Add unit tests for Pulsar source factory discovery and option mapping.
Run Gluten Flink unit tests for the new Pulsar source factory.
Manually verify with local Pulsar standalone:create a Pulsar-backed Flink SQL source table
submit an insert query into a blackhole or print sink
produce records to the Pulsar topic
confirm Flink source metrics and Pulsar subscription stats show records consumed

### Gluten version

None

Start by locating the existing Kafka datasource path and Flink source-factory registration, then trace how source options are mapped into Velox connector parameters. Add factory-discovery and option-mapping unit tests covering the listed Pulsar settings, and run the Gluten Flink unit tests. Done includes a local Pulsar standalone smoke test showing records consumed through a Flink SQL job.

Written by the indexing model from the issue text.