RFR: JDK-8266748: Move modifiers code to Signatures.java [v2]

[Jonathan Gibbons]

On Mon, 7 Jun 2021 13:09:24 GMT, Hannes Wallnöfer <hannesw at openjdk.org> wrote:

>> This change consolidates the code to generate type signature modifiers into `Signatures.TypeSignature`. 
>> 
>> Although this mostly consists of moving the code from `ClassWriterImpl` and `Utils` to `Signatures`, I also avoided the need to split the modifiers string when processing preview modifiers by returning a `List<String>` instead of a `String` in what used to be `Utils.modifiersToString` and is now `TypeSignature.getModifiers`.
>
> Hannes Wallnöfer has updated the pull request incrementally with one additional commit since the last revision:
> 
>   JDK-8266748: Use configuration instead of writer where possible

Generally good, and as with many cleanups, it's a great step in the right direction. As I indicated in a previous round of review, I think that further cleanup is possible (later) by moving more code out of `HtmlDocletWriter` into more specific abstractions, possibly including this one.

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Marked as reviewed by jjg (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/4142