Migrate tests to JUnit5

[strangelookingnerd]

This PR aims to migrate all tests to JUnit5. Changes include:

• Migrate annotations and imports
• Migrate assertions
• Remove public visibility for test classes and methods
• Minor clean up

I am well aware that this is a quite large changeset however I hope that there is still interest in this PR and it will be reviewed.
If there are any questions, please do not hesitate to ping me.

• Make sure you are requesting to pull a topic/feature/bugfix branch (right side) and not your master branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests - that demonstrates feature works or fixes the issue

[strangelookingnerd]

This test was not migrated to JUnit5.

While it would be possible the combination of JenkinsConfiguredWithCodeRule and Envs / Env / EnvsFromFile makes it rather tricky and would require further changes to the tests. As I can not be sure that this would not change the intent of a test, I decided to leave it out of the migration.

[strangelookingnerd]

@jenkinsci/hashicorp-vault-plugin-developers Kindly requesting a review.

[Copilot]

Pull Request Overview

This PR migrates the existing test suite from JUnit4 to JUnit5, updates related imports and annotations, and cleans up test utility classes.

• Converted test classes and lifecycle methods to JUnit Jupiter annotations
• Replaced interface-based constant usage with static imports in utility classes
• Updated project POM to include JUnit Jupiter and Testcontainers JUnit support

Reviewed Changes

Copilot reviewed 30 out of 30 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
VaultTestUtil.java	Updated VaultContainer generics and replaced interface-based constants with static imports
VaultContainer.java	Updated Javadoc for lifecycle hook and replaced deprecated Testcontainers API calls
TestConstants.java	Centralized new constants for JUnit5 tests
MaskingConsoleLogFilterSpec.java	Switched to JUnit5 with MockitoExtension and updated annotations
VaultSecretSourceTest.java	Partial JUnit5 migration; still contains JUnit4 rules and lifecycle annotations
pom.xml	Added Testcontainers JUnit Jupiter dependency and switched Mockito to JUnit Jupiter

Comments suppressed due to low confidence (1)

[dineshba]

Thanks for this PR @strangelookingnerd. LGTM