Add constructor parameter to disable CA pinning

[cisco-annikiti]

Description

Add enableCAPinning option to ClientOptions constructor parameter (default: true).
When disabled, the HTTPS agent validates via OS trust store instead of pinned CAs.
rejectUnauthorized: true is always explicitly set to ensure TLS verification cannot be bypassed regardless of the pinning setting.

Motivation and Context

Provides a configuration option to disable CA pinning for customers who cannot upgrade during a CA bundle transition.

How Has This Been Tested?

Added unit tests covering:

• CA pinning is enabled by default
• CA pinning can be disabled via constructor parameter
• TLS verification is still enforced when CA pinning is disabled

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)