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

[Ben Perez]

Fixed `engineInitSign` in `DSA.java` and added `SecureRandomReset.java` to DSA tests

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Commit messages:
 - Updated copywrite
 - Removed redundant call to getSigningRandom, fixed test formatting
 - Added test for RNG rest
 - Removed misplaced call to getSigningRandom
 - Added RNG reset in initSign

Changes: https://git.openjdk.org/jdk/pull/14273/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14273&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8308474
  Stats: 71 lines in 2 files changed: 70 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/14273.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14273/head:pull/14273

PR: https://git.openjdk.org/jdk/pull/14273