RFR: 8327964: Simplify BigInteger.implMultiplyToLen intrinsic [v7]

[Yudi Zheng]

> Moving array construction within BigInteger.implMultiplyToLen intrinsic candidate to its caller simplifies the intrinsic implementation in JIT compiler.

Yudi Zheng has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains eight additional commits since the last revision:

 - Merge remote-tracking branch 'upstream/master' into JDK-8327964
 - address comments.
 - address comments.
 - address comment.
 - address comment.
 - address comment.
 - address comment.
 - Simplify BigInteger.implMultiplyToLen intrinsic

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Changes:
  - all: https://git.openjdk.org/jdk/pull/18226/files
  - new: https://git.openjdk.org/jdk/pull/18226/files/7c6023f8..c719e0a9

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18226&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18226&range=05-06

  Stats: 560567 lines in 6784 files changed: 132593 ins; 81763 del; 346211 mod
  Patch: https://git.openjdk.org/jdk/pull/18226.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18226/head:pull/18226

PR: https://git.openjdk.org/jdk/pull/18226