RFR: 8366478: BigDecimal roots [v13]

[fabioromano1]

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

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

  Correct procedure for rounding when n < 0

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Changes:
  - all: https://git.openjdk.org/jdk/pull/27148/files
  - new: https://git.openjdk.org/jdk/pull/27148/files/686e0c6b..80b8df3b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27148&range=12
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27148&range=11-12

  Stats: 18 lines in 1 file changed: 8 ins; 3 del; 7 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