samples: Add sample snippets for IN, NOT_EQUALS, and NOT_IN

[jlara310]

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Fixes #738 ☕️

Depends on #688
If you write sample code, please follow the samples format.

[snippet-bot]

Here is the summary of changes.

You are about to add 5 region tags.

• samples/snippets/src/test/java/com/google/datastore/snippets/ConceptsTest.java:1055, tag datastore_eq_query_sorted
• samples/snippets/src/test/java/com/google/datastore/snippets/ConceptsTest.java:1099, tag datastore_in_query
• samples/snippets/src/test/java/com/google/datastore/snippets/ConceptsTest.java:1112, tag datastore_not_equals_query
• samples/snippets/src/test/java/com/google/datastore/snippets/ConceptsTest.java:1125, tag datastore_not_in_query
• samples/snippets/src/test/java/com/google/datastore/snippets/ConceptsTest.java:1138, tag datastore_in_query_sorted

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[jlara310]

Now that #688 is merged, this is also ready for review/merge.

[jlara310]

The project used for testing requires the index below for one of the snippets:

- kind: Task
  properties:
  - name: tag
  - name: tag

Can someone help me add this index to the testing project?

[kolea2]

LGTM with one question. Thanks!

[jlara310]

Looks like ConceptsTest.java runs against the Datastore emulator. The new query operators will not be supported by the emulator any time soon. Not sure how to proceed. Is there a way to run the new tests against a real backend?

[gcf-merge-on-green]

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[jlara310]

Can someone re-trigger the workflows for me again?