[FLINK-34368][fs] Update GCS connector to 3.1.18

[luca-p-castelli]

What is the purpose of the change

Update the GCS file system connector to gcs-connector 3.1.18.

This revives FLINK-34368 now that Flink no longer supports Java 8. The previous attempt (#24267) could not proceed because gcs-connector 3.x requires Java 11 or newer.

Brief change log

• Update gcs-connector from hadoop3-2.2.18 to 3.1.18
• Update the GCS file system documentation links to the new connector version
• Update the bundled dependency entries in flink-gs-fs-hadoop's META-INF/NOTICE

Verifying this change

This change is covered by the existing GCS file system build and test coverage.

Note: I had to make a fix to gcs-connector for version 3.x to have a correct POM.

• gcs-connector 3.x published POM omits dependencies required by the unshaded artifact GoogleCloudDataproc/hadoop-connectors#1744
• Keep gcs-connector published POM full for unshaded artifact GoogleCloudDataproc/hadoop-connectors#1745

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (yes / no) yes
• The public API, i.e., is any changed class annotated with @Public(Evolving): (yes / no) no
• The serializers: (yes / no / don't know) no
• The runtime per-record code paths (performance sensitive): (yes / no / don't know) no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (yes / no / don't know) no
• The S3 file system connector: (yes / no / don't know) no

Documentation

• Does this pull request introduce a new feature? (yes / no) no
• If yes, how is the feature documented? (not applicable / docs / JavaDocs / not documented) not applicable

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Was generative AI tooling used to co-author this PR?

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CI report:

• 89a1165 Azure: FAILURE

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