Retain unique attribute values when consolidating nodes

[gboeing]

This PR resolves #1127 and includes the following enhancements:

• updates the simplification.consolidate_intersections function to retain unique node attribute values when consolidating multiple nodes into one (like how the simplify_graph function does so for unique edge attribute values).
• adds the OSM "junction" and "railway" tags to the default settings.useful_tags_node value to properly capture whether or not a node is a junction (see also https://wiki.openstreetmap.org/wiki/Junctions)
• no longer creates useless "lat" and "lon" node attributes when projecting a graph, because geometry data is consistently stored in the "x" and "y" attributes (or "geometry" attribute as a Shapely Point).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.03%. Comparing base (ea397d3) to head (9de6b89).

❗ Current head 9de6b89 differs from pull request most recent head 06c4ff0. Consider uploading reports for the commit 06c4ff0 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##               v2    #1144   +/-   ##
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  Coverage   98.02%   98.03%           
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  Files          25       25           
  Lines        2433     2438    +5     
=======================================
+ Hits         2385     2390    +5     
  Misses         48       48           

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[gboeing]

The first pre-release OSMnx v2 beta has been released. Testers needed! See #1123 for details.