Walk distance limit applied to bike egress

[ansoncfit]

In the previous R5 release (and maybe earlier ones), bike egress legs appear to be limited to WALK_DISTANCE_LIMIT_METERS (2 km) instead of BIKE_DISTANCE_LIMIT_METERS (5 km).

An exception appears to be around a ~5km treeRebuildZone of modifications that affect the street layer, which can lead to strange looking results. Example with an add-trip modification (in Scenario 1):

In this analysis, a transfer limit of 0 means the added transit line provides no benefit from this origin. The scenario (blue) isochrone has the expected 5 km egress limit for stops within ~5 km of the modification. But egress from all other stops, in both the Baseline and Scenario 1, appears to be limited to 2 km.

[abyrd]

I believe this problem dates back to at least commit a119f60 in August 2019, and seems to have been carried over from before that refactor. The overly simple behavior when calculating base egress tables (not based on an existing linkage) was noticed and commented on at that time. At least on the surface it looks fairly easy to solve, but is located in some code with complicated cacheing behaviors that could have unexpected side effects.