RFR: Add start on a section about logging [v2]

[Jesper Wilhelmsson]

On Mon, 20 Dec 2021 09:24:20 GMT, Ludvig Janiuk <duke at openjdk.java.net> wrote:

>> It's hard to find information on how one should write logging code in Hotspot. This PR is only a first attempt at pointing the reader in the right direction, but a lot could be added in the future:
>>  * In which contexts can one not use unified logging?
>>  * How much should one log?
>>  * What other logging strategies are there?
>
> Ludvig Janiuk has updated the pull request incrementally with one additional commit since the last revision:
> 
>   cleanup

Marked as reviewed by jwilhelm (Lead).

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PR: https://git.openjdk.java.net/guide/pull/70