Fix 6 PVS-Studio static analyzer findings by SufficientDaikon · Pull Request #27035 · PowerShell/PowerShell

Address items 1, 2, 5, 6, 7, 9 from the PVS-Studio report in PowerShell#25289:

- Item 9: Fix ?? operator precedence in StringUtil.cs — appendStr
  length was silently ignored in capacity calculation
- Item 2: Add volatile to logInitialized in CimCmdlets/Utils.cs
  for safe double-checked locking
- Item 6: Move RunspaceRef null check before first use in
  ConsoleHost.cs to prevent NullReferenceException
- Item 1: Add null guard for GetCimInstanceParameter return value
  in CimGetInstance.cs
- Item 5: Use null-conditional on Members["Module"] access in
  ShowCommandCommandInfo.cs
- Item 7: Split vd null check from type check in typeDataQuery.cs
  to prevent NullReferenceException in trace logging

Items 3, 4, 8, 10 are intentionally left — they require design
decisions, affect auto-generated code, or would be breaking changes.

Addresses PowerShell#25289

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>