[ACS-7365] Optimise Search providers and unit tests

[DenysVuika]

Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (check one with "x")

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation
• Other... Please describe:

What is the current behaviour? (You can also link to an open issue here)

What is the new behaviour?

• remove anti-pattern of making public services for the sake of unit testing
• remove the need of SEARCH_QUERY_SERVICE_TOKEN inside the Node Selector component
• remove public accessor workaround from the Node Selector component
• update unit tests not to rely on public component services
• fix issues with injections, do not mark base abstract class as Injectable to avoid problems
• proper setup of the TranslateModule for unit tests, cleanup useless imports

Notes: SEARCH_QUERY_SERVICE_TOKEN is no longer used outside the Content Services library, and can be safely removed

Does this PR introduce a breaking change? (check one with "x")

• Yes
• No

If this PR contains a breaking change, please describe the impact and migration path for existing applications: ...

Other information:
JIRA: ACS-7365

[sonarqubecloud]

Quality Gate failed

Failed conditions
7.1% Duplication on New Code (required ≤ 3%)

See analysis details on SonarCloud