Merge all routing policies into one

[guicassolato]

This is one of the options we have to fix THREESCALE-4016 It corresponds to the first solution proposed in the dev notes.

[codecov]

Codecov Report

Merging #1465 into master will decrease coverage by 27.29%.
The diff coverage is 14.28%.

@@            Coverage Diff             @@
##           master    #1465      +/-   ##
==========================================
- Coverage   90.47%   63.18%   -27.3%     
==========================================
  Files        2252     1509     -743     
  Lines       70471    40928   -29543     
==========================================
- Hits        63760    25861   -37899     
- Misses       6711    15067    +8356

Impacted Files	Coverage Δ
app/lib/backend_api_logic/routing_policy.rb	47.22% <14.28%> (-52.78%)	⬇️
app/indices/account_index.rb	5.55% <0%> (-88.89%)	⬇️
app/indices/topic_index.rb	14.28% <0%> (-85.72%)	⬇️
...pp/controllers/buyers/impersonations_controller.rb	15.38% <0%> (-84.62%)	⬇️
app/lib/csv/applications_exporter.rb	16% <0%> (-84%)	⬇️
config/abilities/buyer_any.rb	5% <0%> (-90%)	⬇️
test/test_helpers/proxy.rb	20% <0%> (-80%)	⬇️
app/indices/proxy_rules_index.rb	20% <0%> (-80%)	⬇️
app/helpers/vertical_nav_helper.rb	12.22% <0%> (-81.67%)	⬇️
app/messengers/plans_messenger.rb	22.22% <0%> (-77.78%)	⬇️
... and 1434 more

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[hallelujah]

rules can be nil in some policies. But agree that for routing it must be an Array

[{"configuration":{},"name":"apicast","version":"builtin","enabled":true},{"configuration":{"rules":[]},"name":"routing","version":"builtin","enabled":true}]