RFR: 8283715: Update ObjectStreamClass to be final

[Roger Riggs]

On Tue, 29 Mar 2022 01:07:33 GMT, Stuart Marks <smarks at openjdk.org> wrote:

> Pretty much just what it says.

Close by is `java.io.ObjectStreamField` which seems also useful to make final.
Though it does have a public constructor so is more likely to raise a compatibility concern.

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PR: https://git.openjdk.java.net/jdk/pull/8009