Request pre-processing, response value assertions, and stateful contract testing.

[StarKhan6368]

What: Examples pre-processing, response value assertions, and stateful contract testing.

Why:

• This enables the substitution of payload data from a custom config or a running entity prior to making requests
• Enables the assertion of response values based on the request, a running entity cache, and additional stores.

How:

• Implement a running entity cache and configuration store.
• Implement substitution from these stores into the requests whenever necessary.
• Create assertions for Equals, NotEquals, If-Then-Else, and array_has operations.
• And more.

Checklist:

• Documentation added to the README.md OR link to PR on https://github.com/specmatic/specmatic-documentation
• Tests
• Sonar Quality Gate