RFR: 8365581: Optimize Java implementation of P256 arithmetic [v4]

[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%.

Ben Perez has updated the pull request incrementally with one additional commit since the last revision:

  removed unnecessary subtraction

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Changes:
  - all: https://git.openjdk.org/jdk/pull/26792/files
  - new: https://git.openjdk.org/jdk/pull/26792/files/a3ddd412..bd7370c1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26792&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26792&range=02-03

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 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