[crac] RFR: Clear JarFileFactory cache on checkpoint [v2]

[Anton Kozlov]

On Tue, 8 Feb 2022 13:37:08 GMT, Anton Kozlov <akozlov at openjdk.org> wrote:

>> Even after an URL object referring to a jar file is closed, the JarFile remains cached and open. This change cleans the cache, so the JarFile becomes reclaimable. The only user of the changed class, sun.net.www.protocol.jar.JarURLConnection, does not assume any state of the cache.
>
> Anton Kozlov has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Avoid beforeCheckpoint race with JarURLConnection.connect()

Thanks for review!

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PR: https://git.openjdk.java.net/crac/pull/14