Added new methods for NAS server support

[ashleyvjoy]

Description

Added 4 new methods - GetNASByName, GetNAS, CreateNAS, DeleteNAS and UTs

GitHub Issues

List the GitHub issues impacted by this PR:

| GitHub Issue # |
| dell/csm#763 |

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

• Tested creation of NAS server on PowerFlex 4.0 array, retrieving NAS server by name and id and deleting NAS server.

=== RUN   TestGetNasByName
=== RUN   TestGetNasByName/success
--- PASS: TestGetNasByName/success (0.00s)
=== RUN   TestGetNasByName/not_found
--- PASS: TestGetNasByName/not_found (0.00s)
--- PASS: TestGetNasByName (0.00s)
=== RUN   TestGetNAS
=== RUN   TestGetNAS/success
--- PASS: TestGetNAS/success (0.00s)
=== RUN   TestGetNAS/not_found
--- PASS: TestGetNAS/not_found (0.00s)
--- PASS: TestGetNAS (0.00s)
=== RUN   TestCreateNAS
=== RUN   TestCreateNAS/bad_request
--- PASS: TestCreateNAS/bad_request (0.00s)
=== RUN   TestCreateNAS/success
--- PASS: TestCreateNAS/success (0.00s)
--- PASS: TestCreateNAS (0.00s)
=== RUN   Test_DeleteNAS
--- PASS: Test_DeleteNAS (0.00s)
PASS
ok      github.com/dell/goscaleio       0.011s

[VamsiSiddu-7]

@ashleyvjoy rebase your branch with main. Some of the changes are already in main. rename the files fs.go and fs_test.go to nfs.go and nfs_test.go

[khareRajshree]

Please add the integration tests for the same as well.

[ashleyvjoy]

Please add the integration tests for the same as well.

Added the integration tests

[ashleyvjoy]

@ashleyvjoy rebase your branch with main. Some of the changes are already in main. rename the files fs.go and fs_test.go to nfs.go and nfs_test.go

Done