[SPARK-36533][SS][FOLLOWUP] Support Trigger.AvailableNow in PySpark

[HeartSaVioR]

What changes were proposed in this pull request?

This PR proposes to add Trigger.AvailableNow in PySpark on top of #33763.

Why are the changes needed?

We missed adding Trigger.AvailableNow in PySpark in #33763.

Does this PR introduce any user-facing change?

Yes, Trigger.AvailableNow will be available in PySpark as well.

How was this patch tested?

Added simple validation in PySpark doc. Manually tested as below:

>>> spark.readStream.format("text").load("/WorkArea/ScalaProjects/spark-apache/dist/inputs").writeStream.format("console").trigger(once=True).start()
<pyspark.sql.streaming.StreamingQuery object at 0x118dff6d0>
-------------------------------------------
Batch: 0
-------------------------------------------
+-----+
|value|
+-----+
|    a|
|    b|
|    c|
|    d|
|    e|
+-----+


>>> spark.readStream.format("text").load("/WorkArea/ScalaProjects/spark-apache/dist/inputs").writeStream.format("console").trigger(availableNow=True).start()
<pyspark.sql.streaming.StreamingQuery object at 0x118dffe50>
>>> -------------------------------------------
Batch: 0
-------------------------------------------
+-----+
|value|
+-----+
|    a|
|    b|
|    c|
|    d|
|    e|
+-----+


>>> spark.readStream.format("text").option("maxfilespertrigger", "2").load("/WorkArea/ScalaProjects/spark-apache/dist/inputs").writeStream.format("console").trigger(availableNow=True).start()
<pyspark.sql.streaming.StreamingQuery object at 0x118dff820>
>>> -------------------------------------------
Batch: 0
-------------------------------------------
+-----+
|value|
+-----+
|    a|
|    b|
+-----+

-------------------------------------------
Batch: 1
-------------------------------------------
+-----+
|value|
+-----+
|    c|
|    d|
+-----+

-------------------------------------------
Batch: 2
-------------------------------------------
+-----+
|value|
+-----+
|    e|
+-----+

>>>

[HeartSaVioR]

cc. @srowen @brkyvz @viirya @xuanyuanking @bozhang2820
Also cc. @HyukjinKwon to double-check I don't miss any rules specific to PySpark side.

[SparkQA]

Test build #145212 has finished for PR 34592 at commit 1f795f4.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[HeartSaVioR]

Thanks for the quick review! Merging to master.

[SparkQA]

Kubernetes integration test starting
URL: https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder-K8s/49681/

[SparkQA]

Kubernetes integration test status failure
URL: https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder-K8s/49681/

[HeartSaVioR]

I forgot about SS guide doc; there're code examples on trigger in PySpark. I'll need to update the doc as well. Crafting another follow-up PR sooner...

[HeartSaVioR]

#34597