RFR: CODETOOLS-7903302: cleanup code

[Iris Clark]

On Tue, 13 Sep 2022 22:05:28 GMT, Jonathan Gibbons <jjg at openjdk.org> wrote:

> Please review a medium-sized update to clean up the jtreg code.
> 
> Most of the changes were performed directly by the IDE. Many of the changes are very local (same line) but some affect surrounding lines when the code was reformatted ... for example, when using lambdas, or try with resources.
> 
> The most "risky" change was converting `Arrays.asList`, which permits `null`, to `List.of`, which does not. This was fixed up manually in a few places, most notable in `ModuleConfig`. In all places, `null` was easily changed to an empty string `""`.

Like that several instances of @SuppressWarnings have been removed/resolved.

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Marked as reviewed by iris (Reviewer).

PR: https://git.openjdk.org/jtreg/pull/118