RFR: 8273147: Update and restructure TestGCLogMessages log message list [v4]

[Thomas Schatzl]

On Thu, 2 Sep 2021 09:39:08 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> Thomas Schatzl has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Move ext root scan subphases to proper location
>
> Marked as reviewed by ayang (Reviewer).

Thanks @albertnetymk @walulyai for your reviews.

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PR: https://git.openjdk.java.net/jdk/pull/5306