[jdk17u-dev] RFR: 8294314: Minimize disabled warnings in hotspot

[Sergey Bylokhov]

Hi all,

This pull request contains a backport of commit [7743345f](https://github.com/openjdk/jdk/commit/7743345f6f73398f280fd18364b4cea10a6b0f2f) from the [openjdk/jdk](https://git.openjdk.org/jdk) repository.

The commit being backported was authored by Magnus Ihse Bursie on 17 Oct 2022 and was reviewed by Erik Joelsson and Aleksey Shipilev.

The patch updates the code to handle certain warnings during compilation. It is part of the ongoing effort to migrate JDK 17 to the new toolchain, including Xcode 16, and will make further patches cleaner.

The patch is not clean because the next two are not in jdk17u:
 - https://bugs.openjdk.org/browse/JDK-8286262 -> still need to disable [4996](https://github.com/openjdk/jdk17u-dev/pull/4143/commits/e1b33bcab3a09bcdf16ea6bd740d4ffbf00adaab) warning
 - https://bugs.openjdk.org/browse/JDK-8293182 -> still need to disable [missing-field-initializers](https://github.com/openjdk/jdk17u-dev/pull/4143/commits/32855c2267dd796d82893f39e82592dc68fef3c6)

The next two are are already in jdk17u so context a little bit different:
 - https://bugs.openjdk.org/browse/JDK-8300169
 - https://bugs.openjdk.org/browse/JDK-8319818


Testing:
 - github actions
 - gcc: 7.3.1, 10.5.0, 11.4.0, 11.5.0 and 13.3.0
 - xcode: 26, 26.0.1
 - VS 2022

-------------

Commit messages:
 - Ignore "missing-field-initializers" in heapShared.cpp, JDK-8293182 is not in 17
 - get back 4996
 - Backport 7743345f6f73398f280fd18364b4cea10a6b0f2f

Changes: https://git.openjdk.org/jdk17u-dev/pull/4143/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=4143&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8294314
  Stats: 68 lines in 5 files changed: 45 ins; 11 del; 12 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/4143.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/4143/head:pull/4143

PR: https://git.openjdk.org/jdk17u-dev/pull/4143