[Bug Fix] Fix snapshot pattern parsing in SM deletion workflow to handle comma-separated values

[Tarun-kishore]

Description

This PR fixes a bug in the Snapshot Management (SM) deletion workflow where comma-separated snapshot patterns are incorrectly passed as a single string to the GetSnapshotsRequest API, causing SnapshotMissingException even when matching snapshots exist in the repository.

Problem:
When an SM deletion policy includes a snapshot_pattern field (e.g., "snp*"), the code concatenates it with the policy name pattern (e.g., "policy-name*,snp*") and passes this as a single string element to the API. OpenSearch's GetSnapshots API then treats "policy-name*,snp*" as a literal snapshot name rather than two separate patterns to match.

Solution:
Modified the getSnapshots(name: String, repo: String) function in SMUtils.kt to split comma-separated patterns into separate array elements before passing them to GetSnapshotsRequest.snapshots().

Changes:

• Updated SMUtils.kt to parse comma-separated snapshot patterns into separate array elements
• Added comprehensive debug logging throughout the SM deletion workflow to aid in troubleshooting
• Added logging in DeletingState.kt, DeletionStartState.kt, DeletionConditionMetState.kt, and DeletionFinishedState.kt

Impact:

• Fixes deletion-only SM policies that use the snapshot_pattern field
• Enables proper lifecycle management of snapshots created outside the policy
• Resolves false positive "No snapshots found" warnings when snapshots exist

Before:

.snapshots(arrayOf("policy-name*,snp*"))  // Single element - incorrect

After:

val patterns = name.split(",").map { it.trim() }.toTypedArray()
.snapshots(patterns)  // Multiple elements: ["policy-name*", "snp*"] - correct

Related Issues

Resolves #1502

Check List

• New functionality includes testing.
• New functionality has been documented.
• API changes companion pull request created.
• Commits are signed per the DCO using --signoff.
• Public documentation issue/PR created.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
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[Tarun-kishore]

@bowenlan-amzn Please review this PR. Tagging you as you have context on feature PR for this.
Thanks

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.49%. Comparing base (3cf62f0) to head (6157137).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1503      +/-   ##
==========================================
+ Coverage   76.47%   76.49%   +0.01%     
==========================================
  Files         375      375              
  Lines       18835    18836       +1     
  Branches     2401     2401              
==========================================
+ Hits        14405    14409       +4     
- Misses       3182     3186       +4     
+ Partials     1248     1241       -7     

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