fix(fsx): stream directory entries in RemoveContents to avoid memory spike on large BN PVs

[Dosik13]

Description

This pull request changes the following:

• pkg/fsx/manager_unix.go — RemoveContents now streams directory entries in bounded
  batches via (*os.File).ReadDir(256) instead of loading the whole listing with
  os.ReadDir, keeping memory usage constant on large block node PVs.
• internal/workflows/steps/step_cluster_uninstall.go — the cleanup-weaver-files step
  uses the same batched read pattern for consistency, preserving its skip-dirs and
  best-effort teardown behavior.
• pkg/fsx/manager_unix_test.go — adds TestUnixManager_RemoveContents_MultipleBatches,
  which exercises the batched loop across more than two full batches.

Related Issues

• Closes fix(fsx): stream directory entries in RemoveContents to avoid memory spike on large BN PVs #363

[swirlds-automation]

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[Copilot]

Pull request overview

This PR updates filesystem cleanup logic to avoid memory spikes when deleting very large directories by switching from os.ReadDir (reads entire listing) to bounded batched reads via (*os.File).ReadDir(256). It applies the same pattern both to fsx.Manager.RemoveContents and to the cluster uninstall cleanup step, and adds a unit test to exercise multi-batch behavior.

Changes:

• Stream directory entries in pkg/fsx/unixManager.RemoveContents using ReadDir(removeContentsBatchSize) batches.
• Update CleanupWeaverFiles to iterate /opt/solo/weaver entries in batches while preserving skip-dirs + best-effort teardown behavior.
• Add TestUnixManager_RemoveContents_MultipleBatches to cover removal across multiple full batches.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
pkg/fsx/manager_unix.go	Reworks RemoveContents to open the directory and remove entries while iterating in fixed-size ReadDir batches.
internal/workflows/steps/step_cluster_uninstall.go	Switches weaver-home cleanup to batched directory reads and keeps teardown best-effort semantics.
pkg/fsx/manager_unix_test.go	Adds a new test ensuring RemoveContents works correctly across multiple ReadDir batches.

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[brunodam]

LGTM