Leverage InstanceConfiguration for Custom Extensions

[nharper285]

[Created for tracking purposes]
The CoSTR Team has worked with MSR to design and implement custom extensions by leveraging the existing OneFuzzInstance Configuration infrastructure.
Initially, the CoSTR team will enable the extensions required for security monitoring. These extensions include the following:

• Geneva Monitoring Extension (Windows)
• Azure Monitor Extension (Linux)
• Azure Security Extension (Linux)
• Azure KeyVault Extension (Windows & Linux)

The feature also includes a generic means by which future custom extensions can be implemented.