RFR: 8256484: ZGC: Rename ZRelocationSetSelector::register_garbage_page()

[Per Liden]

On Tue, 17 Nov 2020 19:25:50 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> This came up in a review of a separate change. `ZRelocationSetSelector::register_garbage_page()` is a slightly misleading name, since "live pages" can also contain garbage. A better name is `ZRelocationSetSelector::register_empty_page()`. To keep the names consistent I propose that we also rename `_registered_pages` to `_live_pages`, to match better `ZRelocationSetSelector::register_live_page()`.
>
> Marked as reviewed by ayang (Author).

Thanks for reviewing!

-------------

PR: https://git.openjdk.java.net/jdk/pull/1264