fix!: remove istio and kalm

[apeabody]

b/459339773

[gemini-code-assist]

Summary of Changes

Hello @apeabody, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a significant breaking change by entirely removing the Istio and KALM addons from the GKE cluster module configurations. The primary purpose is to streamline the module by eliminating features that are either deprecated or no longer supported directly within the module, thereby simplifying cluster management and encouraging migration to more robust, standalone service mesh solutions like Anthos Service Mesh. This change impacts all related variables, outputs, documentation, and test configurations.

Highlights

• Istio and KALM Addon Removal: The Istio and KALM addons, along with all their associated configurations, variables, and outputs, have been completely removed from the GKE cluster definitions across all relevant modules. This includes istio_config, kalm_config, istio, istio_auth, and istio_enabled.
• Migration Guide for v43.0: A new migration guide (docs/upgrading_to_v43.0.md) has been added to detail the breaking changes in v43.0, specifically the removal of kalm_config and Istio-related variables/outputs. It advises users to migrate from the GKE Istio addon to Anthos Service Mesh (ASM) or other service mesh solutions.
• Documentation and Test Updates: All READMEs, metadata files, and integration test data across various modules have been updated to remove references to the deprecated Istio and KALM features, ensuring consistency with the new configuration.
• Cloud Service Mesh Reference: The autogen/safer-cluster/README.md file has been updated to suggest 'Cloud Service Mesh' as an alternative for encrypting and controlling communication between applications, replacing the previous reference to Istio.

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[gemini-code-assist]

Code Review

This pull request removes support for Istio and Kalm configurations across multiple modules and documentation files. The changes are extensive and consistently applied, including the addition of an upgrade guide to inform users about this breaking change. However, the modifications to two JSON files used for integration tests (test/integration/beta_cluster/testdata/TestBetaCluster.json and test/integration/simple_windows_node_pool/testdata/TestSimpleWindowsNodePool.json) have introduced syntax errors that will cause the tests to fail. These errors need to be corrected to ensure the test suite remains valid.

[apeabody]

/gemini review

[gemini-code-assist]

Code Review

This pull request removes the Istio and KALM configurations from the Kubernetes Engine Terraform modules. This is a significant breaking change that is well-documented with a new upgrade guide in docs/upgrading_to_v43.0.md. The changes are comprehensive, touching all relevant modules, autogenerated files, documentation, and test data to reflect the removal of these features. The code modifications consistently remove variables, locals, outputs, and configuration blocks related to Istio and KALM. The documentation has also been updated to point users towards alternative solutions like Anthos Service Mesh. The changes appear to be correct and thoroughly implemented.