RFR: 8343925: Test HugeToString.java crashes at java.util.BitSet.toString()Ljava/lang/String

[Shaojin Wen]

8343925 Feedback PR #21593 test/jdk/java/util/BitSet/HugeToString.java crash, so submit this PR to roll back

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

Commit messages:
 - Revert "8342650: Move getChars to DecimalDigits"

Changes: https://git.openjdk.org/jdk/pull/22012/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22012&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8343925
  Stats: 757 lines in 12 files changed: 352 ins; 381 del; 24 mod
  Patch: https://git.openjdk.org/jdk/pull/22012.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22012/head:pull/22012

PR: https://git.openjdk.org/jdk/pull/22012