…g APQ request

Support null query when running APQ request

Full issue described in graphql-java#4008

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#### AI description  (iteration 1)
#### PR Classification
Bug fix: Enhance ExecutionInput to properly handle null queries in automatic persisted query (APQ) requests.

#### PR Summary
This pull request modifies the ExecutionInput logic to return a persisted query marker when a null or empty query is provided along with a persistedQuery extension, ensuring graceful handling of APQ requests.
- `src/main/java/graphql/ExecutionInput.java`: Introduces a new static method (`assertQuery`) to check for null/empty queries and returns a persisted query marker if appropriate; also removes the strict non-null assertion in the builder.
- `src/test/groovy/graphql/ExecutionInputTest.groovy`: Adds a test case validating that a null query with the persistedQuery extension returns the expected persisted query marker.
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Related work items: #355548

# Conflicts:
#	src/test/groovy/graphql/ExecutionInputTest.groovy