Implement alias command with local and API-connected modes

[InTheCloudDan]

• Add new 'alias' command to CLI with --flag-key flag for local mode
• Create AliasOptions struct with conditional validation logic
• Implement GenerateAliases function supporting both modes:
  • Local mode: generates aliases for single flag key without API
  • API mode: fetches all flags from LaunchDarkly and generates aliases
• Add InitYAMLForAlias to handle configuration without strict preconditions
• Default dir to current working directory when not specified
• Add comprehensive tests for alias options validation
• Update existing tests to reflect new dir defaulting behavior

The alias command now works in two modes:

1. Local: ld-find-code-refs alias --flag-key my-flag
2. API: ld-find-code-refs alias --accessToken <token> --projKey <project>