build(deps): macOS platform dependencies are minimized as much as possible

[0x676e67]

This pull request introduces several changes to add support for macOS system configuration as an optional feature. The most important changes include modifications to the Cargo.toml file to define the new feature and updates to the src/proxy.rs file to conditionally compile code based on the feature flag.

Feature addition in Cargo.toml:

• Added macos-system-configuration to the default features list.
• Defined the macos-system-configuration feature to use the system-configuration dependency.
• Marked the system-configuration dependency as optional for macOS targets.

Conditional compilation in src/proxy.rs:

• Updated the import statement for system_configuration to be conditional on the macos-system-configuration feature.
• Modified the parse_setting_from_dynamic_store and get_from_platform_impl functions to conditionally compile based on the macos-system-configuration feature. [1] [2]
• Adjusted the get_from_platform function to include the feature flag in its conditional compilation.