[Resource Sharing] Use custom action prefixes for sample resource plugin

[cwperks]

Description

Companion core PR: opensearch-project/OpenSearch#20913

This changes in this PR changes the sample actions in the sample-resource-plugin to use the sampleresource: and sampleresourcegroup: prefixes for readability.

• Category (Enhancement, New feature, Bug fix, Test fix, Refactoring, Maintenance, Documentation)

Enhancement

Issues Resolved

Related to #4500

Check List

• New functionality includes testing
• New functionality has been documented
• New Roles/Permissions have a corresponding security dashboards plugin PR
• API changes companion pull request created
• Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.84%. Comparing base (adf4a40) to head (6d97812).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6020      +/-   ##
==========================================
+ Coverage   73.79%   73.84%   +0.04%     
==========================================
  Files         440      440              
  Lines       27259    27332      +73     
  Branches     4052     4073      +21     
==========================================
+ Hits        20117    20182      +65     
  Misses       5227     5227              
- Partials     1915     1923       +8     

Files with missing lines	Coverage Δ
...urce/actions/rest/create/CreateResourceAction.java	100.00% <ø> (ø)
...urce/actions/rest/create/UpdateResourceAction.java	100.00% <ø> (ø)
...urce/actions/rest/delete/DeleteResourceAction.java	100.00% <ø> (ø)
...e/resource/actions/rest/get/GetResourceAction.java	100.00% <ø> (ø)
...urce/actions/rest/search/SearchResourceAction.java	100.00% <ø> (ø)
...actions/rest/create/CreateResourceGroupAction.java	100.00% <ø> (ø)
...actions/rest/create/UpdateResourceGroupAction.java	100.00% <ø> (ø)
...actions/rest/delete/DeleteResourceGroupAction.java	100.00% <ø> (ø)
...group/actions/rest/get/GetResourceGroupAction.java	100.00% <ø> (ø)
...actions/rest/search/SearchResourceGroupAction.java	100.00% <ø> (ø)
... and 1 more

... and 9 files with indirect coverage changes

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