RFR: 8355992: Add some useful "exact" methods to Math and StrictMath

[Raffaello Giulietti]

Add `powExact()` and `unsignedPowExact()` methods that operate on integer values arguments.
Further, add `unsignedMultiplyExact` methods as well.

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Commit messages:
 - 8355992: Add some useful "exact" methods to Math and StrictMath

Changes: https://git.openjdk.org/jdk/pull/25003/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25003&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8355992
  Stats: 324 lines in 2 files changed: 324 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/25003.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25003/head:pull/25003

PR: https://git.openjdk.org/jdk/pull/25003