8357993: Use "stdin.encoding" for reading System.in with InputStreamReader/Scanner [hotspot]

[vy]

Passes the Charset read from the stdin.encoding system property while creating InputStreamReader or Scanner instances for System.in.

stdin.encoding is a recently added property for Java 25 in JDK-8350703. Employing it throughout the entire code base is addressed by the parent ticket JDK-8356893. JDK-8357993 this PR is addressing is a sub-task of JDK-8356893 and is concerned with only areas related to Hotspot.

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Issue

• JDK-8357993: Use "stdin.encoding" for reading System.in with InputStreamReader/Scanner [hotspot] (Sub-task - P4)

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