RFR: 8359395: XML signature generation does not support user provided SecureRandom

[Weijun Wang]

New `XMLSignContext` property to allow user-specific `SecureRandom` for XML signature generation.

-------------

Commit messages:
 - the change

Changes: https://git.openjdk.org/jdk/pull/25802/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25802&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8359395
  Stats: 117 lines in 3 files changed: 115 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/25802.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25802/head:pull/25802

PR: https://git.openjdk.org/jdk/pull/25802