Close InputStreamReader in readProcessStream

[tejas-ae]

While tracing readProcessStream in inject/src/main/java/io/micronaut/context/env/DefaultEnvironmentAndPackageDeducer.java I noticed what might be an issue: The resource opened there can leak if readProcessStream exits on an error path. this patch moves the allocation into try-with-resources so cleanup happens on every exit path. Let me know if the approach doesn’t fit.

Happy to revise the approach or close this if it doesn’t fit — you know the codebase far better than I do.

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