RFR: 8365581: Optimize Java implementation of P256 arithmetic

[Ben Perez]

There are several places where MontgomeryIntegerPolynomialP256.mult() can be optimized. In particular, since modulus[2] = 0 several multiplications can be removed. Other multiplications can be replaced by shifts, which also saves time. Preliminary tests indicate an improvement between 5-10%.

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Commit messages:
 - removed trailing whitespace
 - Merge branch 'openjdk:master' into p256
 - Remove comment
 - remove unnecessary arithmetic operations

Changes: https://git.openjdk.org/jdk/pull/26792/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26792&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8365581
  Stats: 32 lines in 1 file changed: 0 ins; 20 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/26792.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26792/head:pull/26792

PR: https://git.openjdk.org/jdk/pull/26792