OPENNLP-1412 Provide equals and hashCode for ParserModel and TokenizerModel

[mawiesne]

Change

• adds specific equals and hashCode implementations for TokenizerModel and ParserModel.
• introduces new test dependency junit-jupiter-params (test-scoped) to opennlp-tools for more flexible test setups.
• improves TokenizerModelTest, treeinsert.ParserTest and chunking.ParserTest by adding further assertions and fixes TODOs.
• adds AbstractParserModelTest to avoid code duplication, simplifying existing test cases.
• adds another Parse example to demonstrate how easy it is to check different examples without duplicating code.
• removes uncommented code from both ParserTest variants (chunker/treeinsert) by providing actual assertions instead!

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