RFR: 8366478: BigDecimal roots [v30]

[fabioromano1]

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

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

  Added further tests and optimized result assertions

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Changes:
  - all: https://git.openjdk.org/jdk/pull/27148/files
  - new: https://git.openjdk.org/jdk/pull/27148/files/97dbb083..83c4ff53

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27148&range=29
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27148&range=28-29

  Stats: 191 lines in 2 files changed: 89 ins; 30 del; 72 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