Add CA bundle version and CA pinning status to User-Agent string

[cisco-annikiti]

Description

Append ca_bundle/1.0 and (ca_pinning=enabled|disabled) to the User-Agent header string, reflecting the CA bundle version and runtime pinning state

Motivation and Context

Part of the CA Pinning Standardization initiative. Server-side visibility into which CA bundle version clients are using and whether pinning is active helps assess impact scope during certificate-related incidents

How Has This Been Tested?

Added 2 unit tests:

• Verifies User-Agent includes ca_bundle/1.0 and (ca_pinning=enabled) when pinning is on (default)
• Verifies User-Agent includes ca_bundle/1.0 and (ca_pinning=disabled) when pinning is off

Types of Changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)