RFR: JDK-8297032: IGV: shortcut to center selected nodes [v2]

[Tobias Holenstein]

On Tue, 15 Nov 2022 18:27:50 GMT, Roberto Castañeda Lozano <rcastanedalo at openjdk.org> wrote:

> Looks good to me! A nit (up to you whether you want to address it in this PR): you might disable the action when no node is selected, similarly to the node extraction action.

Thanks for the good input @robcasloz ! 

I addressed your suggestion by making `CenterSelectedNodesAction` a `ModelAwareAction` and overriding the `isEnabled()` function: The action is now disabled if no nodes are selected

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PR: https://git.openjdk.org/jdk/pull/11167