refactor: generalise initializers: ketcher_service structure_editors

[harivyasi]

Generalised initializers that load config from a yaml file

Only the validation section is config dependentant.

ensure Rails.application.{structure_editors,ketcher_service} is defined and an instance of ActiveSupport::OrderedOptions, when config/{structure_editors,ketcher_service}.yml: -- is missing or -- is present but nothing defined for the current environment

• add minor validation when loading the config yml

• also resolve #1929: proper key in the yml example file

[github-actions[bot]]

LCOV of commit 2c071a1 during Continuous Integration #2920

Summary coverage rate:
  lines......: 64.1% (13673 of 21315 lines)
  functions..: no data found
  branches...: no data found

Files changed coverage rate: n/a

[github-actions[bot]]

LCOV of commit 0348257 during Continuous Integration #2965

Summary coverage rate:
  lines......: 64.1% (13672 of 21316 lines)
  functions..: no data found
  branches...: no data found

Files changed coverage rate: n/a

[github-actions[bot]]

LCOV of commit 0b2e0f4 during Continuous Integration #3010

Summary coverage rate:
  lines......: 64.2% (13682 of 21318 lines)
  functions..: no data found
  branches...: no data found

Files changed coverage rate: n/a

[github-actions[bot]]

LCOV of commit c868461 during Continuous Integration #3011

Summary coverage rate:
  lines......: 64.2% (13682 of 21318 lines)
  functions..: no data found
  branches...: no data found

Files changed coverage rate: n/a

[github-actions[bot]]

LCOV of commit c942859 during Continuous Integration #3012

Summary coverage rate:
  lines......: 64.2% (13682 of 21318 lines)
  functions..: no data found
  branches...: no data found

Files changed coverage rate: n/a

[github-actions[bot]]

LCOV of commit 2549413 during Continuous Integration #3014

Summary coverage rate:
  lines......: 64.2% (13682 of 21318 lines)
  functions..: no data found
  branches...: no data found

Files changed coverage rate: n/a