Reorganizes the contract tests

What does this MR do and why?

Reorganizes the provider and consumer tests based on the proposed naming convention.

1. Consumer test fixtures, endpoints, and specs folder structure updated to include subfolders to group each appropriately
2. Consumer spec consumer and provider names updated
3. Provider test specs folder renamed to pact_helpers and subfolders introduced to group the helpers appropriately
4. Provider test state folder structure also updated similar to the rest
5. Provider helper consumer and provider name references updated
6. Provider state consumer and provider name references also updated

README files also updated to reflect changes and include new section related to the folder structure direction and also the naming convention.

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.