'Get all shapes' GraphQL query (for rendering lines on map) breaks for large feeds

[landonreed]

Currently in datatools-ui, there is a GraphQL request that is made to show all of a feed's patterns on a map. This breaks down for very large GTFS feeds (like the NL) and becomes slow (5-10 seconds) for large-ish feeds like NYC buses. This problem was partially the inspiration for #125; however, that issue and its PR ended up adding too much complexity in pursuit of too little (or none at all) optimization.

@evansiroky has done some initial benchmarking to isolate some of this problem, but there may need to be some more tests to isolate this problem. The solution is undetermined, but some suggestions have centered on storing some sort of cached or simplified representation of the shapes rather than fetching them all from a GraphQL query for patterns (with nested shapes).

[landonreed]

Rather than using GraphQL for this, I wonder if it might be more effective to just generate vector tiles for all shapes as part of the feed processing step with something like https://github.com/ElectronicChartCentre/java-vector-tile. This might be more appropriate in https://github.com/conveyal/datatools-server, but if other projects using gtfs-lib need this perhaps the code could go here.