Add note about logical and physical cpu numbers calculation

[ChrsMark]

Address the part that was discussed at #1534 (comment).

Changes

Enhance description of system.cpu.physical.count and system.cpu.logical.count as described at #1534 (comment).

Merge requirement checklist

• CONTRIBUTING.md guidelines followed.
• Change log entry added, according to the guidelines in When to add a changelog entry.
  • If your PR does not need a change log, start the PR title with [chore]
• schema-next.yaml updated with changes to existing conventions.