feat(scenario): change_scenario_state method is added

[imcvampire]

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This PR adds a new function to change scenario state.

References

https://wiremock.org/docs/stateful-behaviour/#setting-the-state-of-an-individual-scenario

Submitter checklist

• [x] Recommended: Join WireMock Slack to get any help in #help-contributing or a project-specific channel like #wiremock-java
• [x] The PR request is well described and justified, including the body and the references
• [x] The PR title represents the desired changelog entry
• [x] The repository's code style is followed (see the contributing guide)
• [x] Test coverage that demonstrates that the change works as expected
• [x] For new features, there's necessary documentation in this pull request or in a subsequent PR to wiremock.org