RFR: 8266666: Implementation for snippets [v16]

[Pavel Rappo]

On Wed, 25 Aug 2021 16:00:08 GMT, Pavel Rappo <prappo at openjdk.org> wrote:

>> This PR implements JEP 413 "Code Snippets in Java API Documentation", which hasn't been yet proposed to target JDK 18. The PR starts as a squashed merge of the https://github.com/openjdk/jdk-sandbox/tree/jdk.javadoc/snippets branch.
>
> Pavel Rappo has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Format code closer to the ambient style
>   
>   Makes new constructs look more natural in their context by adopting the surrounding style.

Apologies for the recent series of consecutive force pushes. I had muddled the history with two commits before figured out that my IDE was reformatting doc comments behind my back. Every time I formatted the doc comment, the IDE reformatted it immediately before committing the change to the repo. I've configured the IDE not to do it from now on.

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PR: https://git.openjdk.java.net/jdk/pull/4795