refactor: migrate to nuke/power apps cli/sdk-style projects

[ewingjm]

Purpose

• Cake intellisense was broken due to a mismatch in framework dependencies with one of the Cake.Xrm add-ins. Cake also requires an add-in for intellisense
• The Cake.Xrm add-ins are not yet using OAuth connection strings and can't connect to newly created environments due to WS-Trust being deprecated
• The Cake.Xrm add-ins embed Power Apps SDK assemblies in their packages. Therefore, the Cake.Xrm packages must be updated in line with updates to the SDK packages.
• The build tasks required user credentials to be stored in plaintext environment variables
• The solution projects were not created using the Power Apps CLI and using the CLI is the easiest way to integrate custom controls and their build tasks
• None of the projects were SDK-style, which is much less complex and allows the .csproj files to be edited in VS without unloading first

Approach

• Migrated from Cake to Nuke, which has more lightweight support for CLI tools and does not rely on third-party extensions for intellisense
• Integrated current solutions onto Power Apps CLI style projects using pac solution clone
• Updated build tasks to use Power Apps CLI where possible, eliminating the need to store credentials in environment variables (authentication is handled through pac)
• Migrated to SDK-style projects

TODOs

• Automated test coverage for new code
• Documentation updated (if required)
• Build and tests successful