fix(spanner): Add ARRAY keywords to keywords

[kai5263499]

Fixes #10078

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[harshachinta]

GoogleSQL supported Array functions - https://cloud.google.com/spanner/docs/reference/standard-sql/array_functions

[kai5263499]

GoogleSQL supported Array functions - https://cloud.google.com/spanner/docs/reference/standard-sql/array_functions

This list appears to match what I've added in my PR. Is there something else I should add here?

[harshachinta]

@kai5263499 Please add tests in parse_test.go similar to https://github.com/googleapis/google-cloud-go/pull/9557?

[kai5263499]

@kai5263499 Please add tests in parse_test.go similar to #9557?

I added tests. That led me to remove ARRAY_FILTER because it expects a lambda expression and that would need to be a brand new type for the parser to support. I'll create a separate issue to track the work that needs to be done to support it.