RFR: 8373231: ECDSAOperations::toAffinePoint is redundant

[John Jiang]

`ECDSAOperations::toAffinePoint` should be removed, and `AffinePoint::fromECPoint` should be used instead.

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Commit messages:
 - 8373231: ECDSAOperations::toAffinePoint is redundant

Changes: https://git.openjdk.org/jdk/pull/28691/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28691&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8373231
  Stats: 12 lines in 2 files changed: 0 ins; 8 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/28691.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28691/head:pull/28691

PR: https://git.openjdk.org/jdk/pull/28691