RFR: 8327964: Simplify BigInteger.implMultiplyToLen intrinsic [v6]

[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 incrementally with one additional commit since the last revision:

  address comments.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/18226/files
  - new: https://git.openjdk.org/jdk/pull/18226/files/72ba58ce..7c6023f8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18226&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18226&range=04-05

  Stats: 24 lines in 2 files changed: 0 ins; 0 del; 24 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