RFR: 8077587: BigInteger Roots [v12]

[fabioromano1]

> This PR implements nth root computation for `BigInteger`s using Newton method and optimizes `BigInteger.pow(int)` method.
> [Here is a proof of convergence of the recurrence used.](https://github.com/user-attachments/files/19785045/nth_root_newton_proof_integers.pdf)

fabioromano1 has updated the pull request incrementally with one additional commit since the last revision:

  BigIntegers nth root's initial estimate optimization

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Changes:
  - all: https://git.openjdk.org/jdk/pull/24690/files
  - new: https://git.openjdk.org/jdk/pull/24690/files/48650de2..54ec8f85

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24690&range=11
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24690&range=10-11

  Stats: 28 lines in 1 file changed: 23 ins; 3 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/24690.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24690/head:pull/24690

PR: https://git.openjdk.org/jdk/pull/24690