RFR: 8316964: Security tools should not call System.exit [v2]

[Weijun Wang]

> Remove most `System.exit()` calls in various security tools and only leave one in the `main` method. This paves the way to convert them to JSR 199 tools.

Weijun Wang has updated the pull request incrementally with one additional commit since the last revision:

  let run return int

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Changes:
  - all: https://git.openjdk.org/jdk/pull/15951/files
  - new: https://git.openjdk.org/jdk/pull/15951/files/6e04fac3..ed6d72c7

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15951&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15951&range=00-01

  Stats: 128 lines in 7 files changed: 24 ins; 47 del; 57 mod
  Patch: https://git.openjdk.org/jdk/pull/15951.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15951/head:pull/15951

PR: https://git.openjdk.org/jdk/pull/15951