RFR: 8356891: Some code simplifications for basic BigIntegers' bit operations [v6]

[fabioromano1]

> Some changes in `Biginteger`s' bit operations that increase the code readability and slightly optimize the execution time.

fabioromano1 has updated the pull request incrementally with one additional commit since the last revision:

  make magBitLength() an instance method

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Changes:
  - all: https://git.openjdk.org/jdk/pull/25166/files
  - new: https://git.openjdk.org/jdk/pull/25166/files/d0df9eb2..642461fe

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25166&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25166&range=04-05

  Stats: 36 lines in 1 file changed: 7 ins; 10 del; 19 mod
  Patch: https://git.openjdk.org/jdk/pull/25166.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25166/head:pull/25166

PR: https://git.openjdk.org/jdk/pull/25166