RFR: 8336274: MutableBigInteger.leftShift(int) optimization

[fabioromano1]

This implementation of MutableBigInteger.leftShift(int) optimizes the current version, avoiding unnecessary copy of the MutableBigInteger's value content and performing the primitive shifting only in the original portion of the value array rather than in the value yet extended with trailing zeros.

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Commit messages:
 - Removed trailing whitespace
 - MutableBigInteger.leftShift(int) optimization

Changes: https://git.openjdk.org/jdk/pull/20008/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20008&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8336274
  Stats: 624 lines in 5 files changed: 587 ins; 10 del; 27 mod
  Patch: https://git.openjdk.org/jdk/pull/20008.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20008/head:pull/20008

PR: https://git.openjdk.org/jdk/pull/20008