Kotlin: Do not escape/sanitize quoted enum values

[tajobe]

Stop escaping string enum values in the kotlin generator (#18107)

These values are arbitrary strings and shouldn't be manipulated, but currently get run through the same escape logic as the generated names for such values. I've updated the tests here to assert that the generate name is still appropriately escaped safely while leaving the values raw as intended.

See also #18107 for reproduction YAML.

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[wing328]

lgtm thanks for the fix