RFR: 8336274: MutableBigInteger.leftShift(int) optimization [v12]

[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.

fabioromano1 has updated the pull request incrementally with two additional commits since the last revision:

 - Merge branch 'patchLeftShift' of https://github.com/fabioromano1/jdk into patchLeftShift
 - Added path-targeted tests

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Changes:
  - all: https://git.openjdk.org/jdk/pull/20008/files
  - new: https://git.openjdk.org/jdk/pull/20008/files/09c13c5a..f2c8f35b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20008&range=11
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20008&range=10-11

  Stats: 56 lines in 1 file changed: 54 ins; 0 del; 2 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