AWS Glue - Null values in partition column

Original discussion: https://github.com/aws/aws-sdk-cpp/discussions/2803

It seems like glue isn't handling the getpartitions API correctly where a partition column has null value.
Example below, I am using the aws cli for simiplicity , which gives the same output as the SDK

My table data is structured as below in S3
```
s3://example-bucket/example_table/
├── int_partition_col=null/
│ ├── string_partition_col=null/
│ │ └── data-part-00001.csv
├── int_partition_col=1/
│ ├── string_partition_col=A/
│ │ └── data-part-00002.csv
└── int_partition_col=2/
├── string_partition_col=B/
│ └── data-part-00003.csv

```
```
> aws glue get-partitions --database-name example_db --table-name example_table --expression "(int_partition_col >= 0)" ->
An error occurred (InvalidStateException) when calling the GetPartitions operation: For input string: "null" is not an integer.

> aws glue get-partitions --database-name example_db --table-name example_table --expression "(string_partition_col is null)" -> Returns empty

> aws glue get-partitions --database-name example_db --table-name example_table --expression "(string_partition_col = 'null')"-> works correctly

```
So it seems like the null value is being considered as a string literal? But from the documentation [here](https://docs.aws.amazon.com/glue/latest/webapi/API_GetPartitions.html), it seems IS NULL etc are supported?

Beginne mit der verlinkten Diskussion und der Dokumentation zu AWS Glue GetPartitions. Führe anschließend die drei aws glue get-partitions-Befehle anhand des Beispiel-Partitionslayouts aus. Vergleiche das Verhalten von SDK und CLI und stelle fest, ob die Behandlung von null ein SDK-Problem oder ein Glue-Service-Problem ist; für den Abschluss sind eine bestätigte Diagnose und eine klar abgegrenzte Änderung erforderlich.

Vom Indexierungsmodell aus dem Issue-Text verfasst.