[docker/cli] Split .docker config into separate directories following platform conventions

### ROOT CAUSE The current Docker CLI configuration does not adhere to platform-specific conventions for storing configuration, data, cache, and runtime files. This leads to inconsistencies across different operating systems and may conflict with system policies or user expectations. ### CODE FIX The fix involves restructuring the Docker CLI directory structure to align with platform conventions: 1. **Unix (XDG Base Directory Specification)**: - Configuration: `$XDG_CONFIG_HOME/docker` - Data: `$XDG_DATA_HOME/docker` - Cache: `$XDG_CACHE_HOME/docker` - Runtime: `$XDG_RUNTIME_DIR/docker` 2. **Windows**: - Configuration: `%APPDATA%\Docker` - Data: `%LOCALAPPDATA%\Docker` - Cache: `%LOCALAPPDATA%\Docker\Cache` - Runtime: `%TEMP%\Docker` 3. **macOS**: - Configuration: `~/Library/Preferences/Docker` - Data: `~/Library/Application Support/Docker` - Cache: `~/Library/Caches/Docker` - Runtime: `/var/folders/*/Docker` (user-specific) **Implementation**: - Update the Docker CLI code to use platform-specific environment variables and paths (e.g., `os.Getenv("XDG_...")` in Go). - Replace hardcoded paths like `~/.docker` with the new structure. - Add migration logic to preserve existing data during the transition. - Update documentation to reflect new directory locations. **Example Code Snippet** (Go): ```go func getConfigDir() string { if runtime.GOOS == "windows" { return filepath.Join(os.Getenv("APPDATA"), "Docker") } // Unix and macOS use XDG or legacy paths if xdgConfig := os.Getenv("XDG_CONFIG_HOME"); xdgConfig != "" { return filepath.Join(xdgConfig, "docker") } return filepath.Join(os.Getenv("HOME"), ".docker") } ``` This solution ensures cross-platform consistency and better system integration.