Split itinerary checks into threads

[br648]

Checklist

• Appropriate branch selected (all PRs must first be merged to dev before they can be merged to master)
• Any modified or new methods or classes have helpful JavaDoc and code is thoroughly commented
• The description lists all applicable issues this PR seeks to resolve
• The description lists any configuration setting(s) that differ from the default settings
• All tests and CI builds passing

Description

This PR attempts to address the bottleneck with making OTP requests for checking itineraries by replacing the existing process with multi-threading.

[binh-dam-ibigroup]

Can we reuse OTP_SERVER_REQUEST_TIMEOUT_IN_SECONDS from OtpDispatcher and make that configurable?

[binh-dam-ibigroup]

Significantly better response saving trips on complicated graphs! Just one nit in the example YML file.