fix(datastore-v1): correct the filter predicate logic applied to optional fields

[5d]

Issue #

Description

The GraphQL filter predication not working properly on optional field. It always return false on optional field with value nil.

General Checklist

• Added new tests to cover change, if needed
• Build succeeds with all target using Swift Package Manager
• All unit tests pass
• All integration tests pass
• Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)
• Documentation update for the change if required
• PR title conforms to conventional commit style
• New or updated tests include Given When Then inline code documentation and are named accordingly testThing_condition_expectation()
• If breaking change, documentation/changelog update with migration instructions

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[lawmicha]

[nit] let's add either a test comment or improve the test name to testBooltruenotEqualBoolNil it's not immediately obvious that the instance has a nil Bool due to the default parameter value. Here and other tests that have similar changes