Add --enable-snapshot-compression flag to control snapshot compression

[Copilot]

What type of PR is this?

/kind feature

What this PR does / why we need it:

Adds --enable-snapshot-compression driver parameter to control whether gzip compression is applied when creating volume snapshots. Users storing already-compressed data can set this to false to skip redundant compression, significantly speeding up snapshot creation and restoration.

Changes:

• Add EnableSnapshotCompression to DriverOptions and Driver structs
• Add --enable-snapshot-compression CLI flag (default: true)
• Update CreateSnapshot to use .tar or .tar.gz based on setting
• Update copyFromSnapshot to auto-detect archive format for backward compatibility
• Add Helm chart support via controller.enableSnapshotCompression

Usage:

# Disable compression for pre-compressed data
--enable-snapshot-compression=false

# Helm values
controller:
  enableSnapshotCompression: false

Which issue(s) this PR fixes:

Fixes #891

Special notes for your reviewer:

• Default true preserves existing behavior
• Snapshot restoration auto-detects format (tries .tar.gz first, then .tar) ensuring backward compatibility with existing compressed snapshots
• Both Go library (TarPack/TarUnpack) and external tar command paths updated

Does this PR introduce a user-facing change?:

Add --enable-snapshot-compression flag to control whether gzip compression is performed when creating volume snapshots. Set to false to skip compression for volumes containing already-compressed data.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Add a parameter to control whether compression is performed when creating volumesnapshots.</issue_title> <issue_description>Is your feature request related to a problem?/Why is this needed

I stores some large compressed files with PVCs. Creating volumesnapshot would compress those files again that is very time-consuming and the compression effect is quite limited.

Describe the solution you'd like in detail

Add a driver parameter to control whether compression is performed when creating volumesnapshots. If no compression，snapshot-controller would do tar (untar) without -z when creating (restoring) a volumesnapshot.

</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes kubernetes-csi/csi-driver-nfs#998

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: Copilot Once this PR has been reviewed and has the lgtm label, please ask for approval from andyzhangx. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment Approvers can cancel approval by writing /approve cancel in a comment