Fix deserialization issue when parameter value is array

[strufkin]

Context

If you have custom converter which makes an array from parameter string from feature file, allure will throw below exception upon report generation, hence we have to make this to be string back:

Could not read test result file allure\e3769575-aa8f-404e-9068-732f53e6db7c-result.json
com.fasterxml.jackson.databind.exc.MismatchedInputException: 
Cannot deserialize value of type `java.lang.String` from Array value (token `JsonToken.START_ARRAY`)
 at [Source: (sun.nio.ch.ChannelInputStream); line: 1, column: 15070] 
 (through reference chain: io.qameta.allure.model.TestResult["parameters"]->java.util.ArrayList[2]->io.qameta.allure.model.Parameter["value"])
        at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:59)

Checklist

• [x] Sign Allure CLA
• [x] Provide unit tests

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