Add validation for directions.txt

[philip-cline]

Checklist

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

Description

It has recently been pointed out that a lack of route records in the GTFS+ directions.txt can cause direction data to become unavailable in downstream systems. This PR provides validation of the GTFS+ directions.txt table to ensure that every route has a corresponding entry.

[philip-cline]

Updated this to match the latest language in the MTC branch. Should be the same as that previously closed PR.

Note if you're testing this you should merge dev into this branch to get the latest updates