Use NPM to download Functions core tools for tests

[ahmedmuhsin]

This pull request updates the installation process for Azure Functions Core Tools in the build.ps1 script. Instead of downloading and extracting a zip file manually, the script now installs the tools globally via npm and then copies the necessary files into the expected directory structure. This change streamlines the setup process and leverages npm for version management.

Core Tools installation process update:

• Replaces manual download and extraction of Azure Functions Core Tools with a global npm installation, simplifying the setup and ensuring the latest version is used.
• After npm installation, copies the CLI payload from the global npm module directory into the local Azure.Functions.Cli directory, maintaining compatibility with existing test layouts.