RFR: 8366478: BigDecimal roots [v29]

[fabioromano1]

> An implementation of `BigDecimal.nthRoot(int, MathContext)`.

fabioromano1 has updated the pull request incrementally with two additional commits since the last revision:

 - Correct for loop of precision in two digit tests
 - Added one digit tests to cover new paths

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Changes:
  - all: https://git.openjdk.org/jdk/pull/27148/files
  - new: https://git.openjdk.org/jdk/pull/27148/files/1f773b38..97dbb083

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27148&range=28
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27148&range=27-28

  Stats: 55 lines in 2 files changed: 21 ins; 14 del; 20 mod
  Patch: https://git.openjdk.org/jdk/pull/27148.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27148/head:pull/27148

PR: https://git.openjdk.org/jdk/pull/27148