Test cases for routing table tests were added:

  * test cases with dropping/resuming all nodes were added;
  * test cases with dropping/resuming several nodes were modified: we drop only
  one node now;
  * test with checking that there are no boundary entries in a routing table
  without any entry about any node was added;
Test case with checking node with one backend was added.
Tests skipping was replaced with conditional test logic (code smell).
Routing table tests cases were added and some small changes:

  * `backends_enabled` parameter was added
  (it's possible to specify backends' **enable** option with this parameter)
  * config indention was corrected
  (indention of config template was corrected and indention of produced config
  was corrected as well)
Test runner was updated and test configs for routing table tests were udpated.

  * test runner was updated with new config format feature
  (it is possible to specify multiple runnings for the same configuration of
  test environment in the same config)
  * redundant comment symbols was removed from default yml parameters file
  * test configs for routing table tests were updated
  (a lot of duplications were removed)
  * descriptions for routing table tests were added to configs files
Some test packs were merged to speed up tests w/o making them fragile/erratic.

  * test descriptions were updated to improve readability
Test configs were updated with new test runner config format.
Test case with concomitant changing backends states was added.
Added case with changing backends states and corrected descriptions.
Merge branch 'v2.26' into features/routing-tests-2