Add common function to make object names filename safe

[webtonize]

Story

As an end-user I want to be sure all my Azure DevOps objects can be exported, even if I have special characters in the object names so I can be sure my complete Azure DevOps environment will get audited and I will not be surprised in human audit.

Acceptance Criteria

• Non-filesystem characters in input Object Names should be replaced by safe characters
• String replacement function should be a single function called from Export- functions
• Export- functions should be changed to use the new function
• When exporting object names, any folder hierarchy in Azure DevOps (like pipeline and release folder structure) should be preserved in the exported filename
• Azure DevOps test project and test cases should reflect handling with and without a folder structure for those objects