[jdk18u] RFR: 8281181: Do not use CPU Shares to compute active processor count

[Ioi Lam]

Please review this backport of [JDK-8281181](https://bugs.openjdk.java.net/browse/JDK-8281181) to jdk18u. Most changes were cleanly applied, except:

- The changes in related to the deprecation of `UseContainerCpuShares` and `PreferContainerQuotaForCPUCount`) have been dropped. That's because the deprecation happens in the JDK 19 release cycle, not in 18u.

You can compare with the JDK 19 version of the changes [here](https://github.com/openjdk/jdk/pull/7666/files). 

Tested with tiers 1-5, including all container test tasks.

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Commit messages:
 - reverted changes to PreferContainerQuotaForCPUCount
 - 8281181: Do not use CPU Shares to compute active processor count

Changes: https://git.openjdk.java.net/jdk18u/pull/78/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk18u&pr=78&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8281181
  Stats: 43 lines in 4 files changed: 28 ins; 0 del; 15 mod
  Patch: https://git.openjdk.java.net/jdk18u/pull/78.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk18u pull/78/head:pull/78

PR: https://git.openjdk.java.net/jdk18u/pull/78