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

I agree with Ludvig here, the guide has never been strictly about process only. Guidelines for how to clone the source code and examples of shell scripts to help development are very hands-on examples of content that has been in the Guide since the first version.

I'm going to allow this section. If it turns out that we have a lot of area specific content that makes the Guide difficult to overview we can (and should) split it into separate documents later.

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