Add support for specifying the `max_items` parameter for pay-per result Actors and their runs #86

Job	Run time
Run lint and type checks / Lint and type checks (3.8)	51s
Run lint and type checks / Lint and type checks (3.9)	1m 4s
Run lint and type checks / Lint and type checks (3.10)	1m 1s
Run lint and type checks / Lint and type checks (3.11)	1m 4s
Check whether the documentation is up to date / Check whether documentation is up-to-date	51s
Run unit tests / Run unit tests (ubuntu-latest, 3.8)	57s
Run unit tests / Run unit tests (ubuntu-latest, 3.9)	53s
Run unit tests / Run unit tests (ubuntu-latest, 3.10)	39s
Run unit tests / Run unit tests (ubuntu-latest, 3.11)	54s
Run unit tests / Run unit tests (windows-latest, 3.8)	1m 45s
Run unit tests / Run unit tests (windows-latest, 3.9)	2m 50s
Run unit tests / Run unit tests (windows-latest, 3.10)	1m 58s
Run unit tests / Run unit tests (windows-latest, 3.11)	2m 16s
Run integration tests / Run integration tests (3.8)	45s
Run integration tests / Run integration tests (3.9)	3m 24s
Run integration tests / Run integration tests (3.10)	39s
Run integration tests / Run integration tests (3.11)	51s
	22m 42s

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