RFR: 8354522: Clones of DecimalFormat cause interferences when used concurrently [v7]

[Johannes Graham]

> The `DigitList` class used in `DecimalFormat` does not reset the `data` array in its clone method. This can cause interference when clones are used concurrently.

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

  reflective test

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/24598/files
  - new: https://git.openjdk.org/jdk/pull/24598/files/abda88ef..87e652be

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24598&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24598&range=05-06

  Stats: 66 lines in 1 file changed: 64 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/24598.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24598/head:pull/24598

PR: https://git.openjdk.org/jdk/pull/24598