RFR: 8366478: BigDecimal roots [v18]

[fabioromano1]

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

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

  Speed up root inversion by computing result's scale before inversion

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Changes:
  - all: https://git.openjdk.org/jdk/pull/27148/files
  - new: https://git.openjdk.org/jdk/pull/27148/files/ee2d762a..7d99c4fc

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27148&range=17
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27148&range=16-17

  Stats: 14 lines in 1 file changed: 1 ins; 8 del; 5 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