Implement VCRReplaySearch modes: SearchAll, SkipFound

[mksh]

Initial implementation was always skipping records which were already found when replaying.

While this provides more strict testing approach, it is only suitable when requests are coming in a predefined order.
If some requests are started in parallel, responses can come in random order too, and so skipping requests
will break the tests.

This PR adds method .with_search(search_mode) and two search modes:

• VCRReplaySearch::SkipFound -- skips found requests on subsequent replays, as default
• VCRReplaySearch::SearchAll -- always goes through all requests and returns first match

Now, tests for parallel requests can work as long as all parallel requests are having different parameters, headers or urls.