[jdk17u-dev] RFR: 8272541: Incorrect overflow test in Toom-Cook branch of BigInteger multiplication

[Andrew John Hughes]

Clean backport. As @shipilev notes on the bug, the original code (JDK-8200659) was backported to all active branches in the January 2019 security update, so we should update the test everywhere as well.

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Commit messages:
 - Backport d1aeca117ccc4334d67b2692ff087a9f8d808a59

Changes: https://git.openjdk.java.net/jdk17u-dev/pull/154/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk17u-dev&pr=154&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8272541
  Stats: 30 lines in 2 files changed: 18 ins; 3 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk17u-dev/pull/154.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17u-dev pull/154/head:pull/154

PR: https://git.openjdk.java.net/jdk17u-dev/pull/154