[jdk21u] RFR: 8308474: DSA does not reset SecureRandom when initSign is called again

[Aleksey Shipilev]

Clean backport to improve DSA security.

Additional testing:
 - [x] New regression test fails without the patch, passes with it

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Commit messages:
 - Backport bed9161c815b5b4773f36eac7e8dadc1384c7fd1

Changes: https://git.openjdk.org/jdk21u/pull/54/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u&pr=54&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8308474
  Stats: 70 lines in 2 files changed: 69 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk21u/pull/54.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u.git pull/54/head:pull/54

PR: https://git.openjdk.org/jdk21u/pull/54