Update CreateSnapshot to conform to CSI 1.6 Spec

[suryagupta4]

Description

This PR addresses the following CSI Spec test scenarios for CreateSnapshot:

• should succeed when requesting to create a snapshot with already existing name and same source volume ID
• should fail when requesting to create a snapshot with already existing name and different source volume ID
• should succeed when creating snapshot with maximum-length name

GitHub Issues

List the GitHub issues impacted by this PR:

GitHub Issue #
dell/csm#1896

Checklist:

• I have performed a self-review of my own code to ensure there are no formatting, vetting, linting, or security issues
• I have verified that new and existing unit tests pass locally with my changes
• I have not allowed coverage numbers to degenerate
• I have maintained at least 90% code coverage
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• Backward compatibility is not broken

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Please also list any relevant details for your test configuration

• Executed SnapSuite (with and w/o Auth enabled) - cert-csi test snap --sc isilon --vsc isilon-snapclass

• csi-sanity for CreateSnapshot - ./csi-sanity --csi.endpoint=unix:///root/csi.sock --ginkgo.focus='CreateSnapshot'

• Executed Auth v2 e2e - all scenarios
  TestSnapshot:
  

[github-actions]

Merging this branch will not change overall coverage

Impacted Packages	Coverage Δ	🤖
github.com/dell/csi-powerscale/common/utils	0.00% (ø)
github.com/dell/csi-powerscale/service	0.00% (ø)

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Coverage by file

Changed files (no unit tests)

Changed File	Coverage Δ	Total	Covered	Missed	🤖
github.com/dell/csi-powerscale/common/utils/utils.go	0.00% (ø)	0	0	0
github.com/dell/csi-powerscale/service/controller.go	0.00% (ø)	0	0	0
github.com/dell/csi-powerscale/service/service.go	0.00% (ø)	0	0	0

Please note that the "Total", "Covered", and "Missed" counts above refer to code statements instead of lines of code. The value in brackets refers to the test coverage of that file in the old version of the code.

Changed unit test files

• github.com/dell/csi-powerscale/common/utils/utils_test.go
• github.com/dell/csi-powerscale/service/service_test.go