Fix sample type policies not being applied when created from templates or fair data station

[stuzart]

• fix for When creating sample type from template or FDS rdf, the specific sharing permissions aren't applied #2219

[Copilot]

Pull Request Overview

This PR refactors the sample type creation workflow to use a shared build_sample_type helper in the controller and updates functional tests to pass and verify policy_attributes and tags for sample types created via various paths.

• Introduce build_sample_type to DRY up controller actions
• Update tests to include policy_attributes and assertions for policies and tags
• Ensure template- and Fair Data Station–based creation also applies sharing policies and tags

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
test/functional/sample_types_controller_test.rb	Added SharingFormTestHelper; pass policy_attributes and tags in test params; added assertions for policy and tags
app/controllers/sample_types_controller.rb	Extracted sample type initialization into build_sample_type; replaced inline setup in create, build_from_template, and TTL actions