RFR: 8318915: Enhance checks in BigDecimal.toPlainString() [v2]

[Raffaello Giulietti]

> Prevent a `NegativeArraySizeException` in `BigDecimal.toPlainString()`, throwing `OutOfMemoryError` instead to indicate that the resulting `String` would be too large.

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

  Using repeat() instead of loop.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/16457/files
  - new: https://git.openjdk.org/jdk/pull/16457/files/cea48148..8a3c0a96

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16457&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16457&range=00-01

  Stats: 9 lines in 1 file changed: 0 ins; 5 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/16457.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16457/head:pull/16457

PR: https://git.openjdk.org/jdk/pull/16457