RFR: 8366478: BigDecimal roots [v7]

[fabioromano1]

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

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

 - Merge branch '8366478' of https://github.com/fabioromano1/jdk into 8366478
 - Restore changes

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Changes:
  - all: https://git.openjdk.org/jdk/pull/27148/files
  - new: https://git.openjdk.org/jdk/pull/27148/files/867e669f..f7ca3421

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27148&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27148&range=05-06

  Stats: 281 lines in 1 file changed: 93 ins; 118 del; 70 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