RFR: 8333578: Fix uses of overaligned types induced by ZCACHE_ALIGNED [v2]

[Axel Boldt-Christmas]

> The only directly heap allocated, constructed object of types that are overaligned because of ZCACHE_ALIGNED is ZCollectedHeap. The other are either in static storage or contained in (and constructed as part of) ZCollectedHeap. So we only need to fix ZCollectedHeap allocation. 
> 
> As the CollectedHeap is only ever created once and is never destroyed, we can simply align the allocation and create an unfreeable pointer.
> 
> This implementation imposes that `ZCacheLineSize` is a power of two, but we already have this requirement elsewhere (e.g. `ZContendedStorage`).
> 
> Testing:
>  * tier 1 through tier 5 Oracle supported platforms
>  * GHA

Axel Boldt-Christmas has updated the pull request incrementally with one additional commit since the last revision:

  Updated comment

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/23885/files
  - new: https://git.openjdk.org/jdk/pull/23885/files/2c13edcd..0b918f00

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23885&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23885&range=00-01

  Stats: 4 lines in 1 file changed: 1 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/23885.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23885/head:pull/23885

PR: https://git.openjdk.org/jdk/pull/23885