More API streamlining for v2

[gboeing]

Resolves #1142. Deprecations for v1 to prep for these changes are in #1146. This PR:

• moves the utils_graph module's get_digraph, get_undirected, graph_to_gdfs, and graph_from_gdfs functions to a new convert module that houses data type converters
• moves the utils_graph module's remove_isolated_nodes and get_largest_component functions to the truncate module
• moves the utils_graph module's route_to_gdf function to the routing module
• move the speed module's functionality to the routing module
• deletes the now-empty utils_graph and speed modules
• renames the functions get_largest_component -> largest_component, get_undirected -> to_undirected, and get_digraph -> to_digraph

[codecov]

Codecov Report

Attention: Patch coverage is 95.65217% with 6 lines in your changes are missing coverage. Please review.

Project coverage is 97.98%. Comparing base (b77689b) to head (550598d).

Files	Patch %	Lines
osmnx/routing.py	91.04%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##               v2    #1148      +/-   ##
==========================================
- Coverage   97.99%   97.98%   -0.01%     
==========================================
  Files          25       24       -1     
  Lines        2440     2432       -8     
==========================================
- Hits         2391     2383       -8     
  Misses         49       49              

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[gboeing]

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