Enable experimental OPEN_API_3_1 support for schematesis; Update openapi.json look up logic

[afonsobspinto]

Closes https://metacell.atlassian.net/browse/CH-178

Implemented solution

• Enables experimental OPEN_API_3_1 support for schematesis;
• Updates look up for openapi.json logic (tries local file then / and on failure /api)
• Adds schemathesis hook to filter out unsafe path parameters

How to test this PR

✦ ❯ harness-test . -i {application} -a

Sanity checks:

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• In this PR it is explicitly stated how to test the current change
• The labels in the issue set the scope and the type of issue (bug, feature, etc.)
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Breaking changes (select one):

• The present changes do not change the preexisting api in any way
• This PR and the issue are tagged as a breaking-change and the migration procedure is well described above

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• There is no reason why deployments based on CloudHarness may break after the current update
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Test coverage (select one):

• Tests for the relevant cases are included in this pr
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Documentation (select one):

• The documentation has been updated to match the current changes
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[afonsobspinto]

Thanks for the review @Stranger6667 👍