RFR: 8284105: Update security libraries to use sealed classes

[Joe Darcy]

On Fri, 8 Apr 2022 13:40:37 GMT, Sean Mullan <mullan at openjdk.org> wrote:

> Please review these changes to update the security libraries to use sealed classes. See JEP 409 for more details on sealed classes.
> 
> No CSR is required as all the changes are to internal classes. A few classes that did not have subclasses were simply marked final instead of sealed.

Marked as reviewed by darcy (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/8165