Add more tests for constants in tree-sitter grammar

[sadikovi]

Requirements

• Filling out the template is required. Any pull request that does not include enough information to be reviewed in a timely manner may be closed at the maintainers' discretion.
• All new code requires tests to ensure against regressions

Description of the Change

The PR adds more tests for various types of constants in situations when they are used as class fields, method names, field names, and in switch statements.

Alternate Designs

N/A

Benefits

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Possible Drawbacks

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Applicable Issues