RFR: 7903156: remove jopt-simple dependency from jextract [v2]

[Athijegannathan Sundararajan]

> removed jopt-simple dependency as well as moditect grade plugin dependency. Piggybacking build.gradle change to enforce 'jtreg_home' check in jtreg task's doFirst block.

Athijegannathan Sundararajan has updated the pull request incrementally with one additional commit since the last revision:

  removed unused java.prefs module

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Changes:
  - all: https://git.openjdk.java.net/jextract/pull/19/files
  - new: https://git.openjdk.java.net/jextract/pull/19/files/e557fb42..066245bf

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jextract&pr=19&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jextract&pr=19&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod
  Patch: https://git.openjdk.java.net/jextract/pull/19.diff
  Fetch: git fetch https://git.openjdk.java.net/jextract pull/19/head:pull/19

PR: https://git.openjdk.java.net/jextract/pull/19