RFR: 8355992: Add unsignedMultiplyExact and *powExact methods to Math and StrictMath [v2]

[Raffaello Giulietti]

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

Raffaello Giulietti has updated the pull request incrementally with one additional commit since the last revision:

  Clearer and more complete spec of the *pow* methods.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/25003/files
  - new: https://git.openjdk.org/jdk/pull/25003/files/9ab1add2..2d3405f2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25003&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25003&range=00-01

  Stats: 24 lines in 2 files changed: 8 ins; 0 del; 16 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