added gating for user preferences for auto imports

[johnfav03]

Implements and tests User Preferences for Auto Imports; the specific preferences included are shown below.

importModuleSpecifierPreference: "shortest" | "project-relative" | "relative" | "non-relative"; importModuleSpecifierEnding: "auto" | "minimal" | "index" | "js"; includePackageJsonAutoImports: "auto" | "on" | "off"; allowRenameOfImportPath: boolean; autoImportFileExcludePatterns: string[]; autoImportSpecifierExcludeRegexes: string[]; preferTypeOnlyAutoImports: boolean;