ENH: new `page_length` parameter for execute_query

Summary

Related issue: https://gitlab.indiscale.com/caosdb/customers/geomar/management/-/issues/159

Focus

• Everything is designed to be used with list comprehension features. See usage examples in caosdb-pyinttest!65 (merged)
• The execute/execute_query functions will now return a Container, an integer or a generator for Containers depending on the parameters.

Test Environment

Tests in caosdb-pyinttest!65 (merged)

Check List for the Author

• All automated tests pass
• Reference related issues
• Up-to-date CHANGELOG.md (or not necessary)
• Up-to-date JSON schema (or not necessary)
• Appropriate user and developer documentation (or not necessary)
  • How do I use the software? Assume "stupid" users.
  • How do I develop or debug the software? Assume novice developers.
• Annotations in code (Gitlab comments)
  • Intent of new code
  • Problems with old code
  • Why this implementation?

Check List for the Reviewer

• I understand the intent of this MR
• All automated tests pass
• Up-to-date CHANGELOG.md (or not necessary)
• Appropriate user and developer documentation (or not necessary)
• The test environment setup works and the intended behavior is reproducible in the test environment
• In-code documentation and comments are up-to-date.
• Check: Are there specifications? Are they satisfied?

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