feat(routing/none): remove nil router

[aschmahmann]

Closes #620

This removes the nil router, if people would prefer something less harsh (e.g. deprecation followed by removal, stubbing followed by deprecation + removal) comment on the issue above

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 60.53%. Comparing base (aaf9a04) to head (7e1497e).

@@            Coverage Diff             @@
##             main     #621      +/-   ##
==========================================
+ Coverage   59.67%   60.53%   +0.86%     
==========================================
  Files         239      238       -1     
  Lines       29961    29537     -424     
==========================================
+ Hits        17879    17881       +2     
+ Misses      10460    10034     -426     
  Partials     1622     1622              

see 33 files with indirect coverage changes