[DOP-22425] Do not run tests as admin DB users

[dolfinus]

Change Summary

• Replace Github Actions services: with explicit docker compose usage. This allows to use the same DB settings in both CI and local environment, without copy-pasting.
• Add healthchecks to almost all containers (except SFTP), to ensure that containers are ready before running any tests.
• For MongoDB and Greenplum instead of connecting to DB as owner, create a dedicated user with permissions only for test schema. This allows to catch errors then connector is trying to access tables/objects which is shouldn't. Discovered issue with MongoDB connection url format, fixed.
• For Oracle 11.2.x tests were flaky because Oracle XE has quite small limit on process number, increased it using custom .sql file.

Related issue number

Checklist

• Commit message and PR title is comprehensive
• Keep the change as small as possible
• Unit and integration tests for the changes exist
• Tests pass on CI and coverage does not decrease
• Documentation reflects the changes where applicable
• docs/changelog/next_release/<pull request or issue id>.<change type>.rst file added describing change
  (see CONTRIBUTING.rst for details.)
• My PR is ready to review.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.47%. Comparing base (10e221c) to head (91e72c4).
Report is 1 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #347   +/-   ##
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  Coverage    92.47%   92.47%           
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  Files          228      228           
  Lines         9875     9880    +5     
  Branches      1013     1013           
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+ Hits          9132     9137    +5     
  Misses         556      556           
  Partials       187      187           

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