RFR: 8293499: Provide jmod --compress option [v6]

[Aleksey Shipilev]

On Tue, 13 Sep 2022 17:41:04 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> I have been looking into `make clean-images images` performance, and realized jmod keeps compressing files with default compression level. Tuning that toward lighter compression levels improves build performance considerably, without a heavy loss in *.jmod sizes. 
>> 
>> This PR allows JMOD to select the compression level. Follow-ups would use this in the build system, see #10214.
>> 
>> The interesting asymmetry against `jlink` is: `jlink` provides `--compress` option that only takes `2` for "ZIP compression". (Separately, we could argue if it would be beneficial to extend `--compress` to `jlink` as well, so to select the compression level there too.)
>
> Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Mention the default level

(posting a comment in the hopes that bots would check the CSR state)

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PR: https://git.openjdk.org/jdk/pull/10213