Refactor build_raw_with_command for improved clarity

[SatoshiQaziMuhammed]

This commit refactors the overly complex build_raw_with_command function in chain_spec.rs by extracting its responsibilities into smaller, focused helper methods. This improves code maintainability and readability.

Changes:

• Introduced ChainSpecPaths struct to encapsulate the three different path contexts (local, in_pod, in_args) used during chain spec generation
• Extracted get_command_ref() and get_plain_path_ref() for cleaner error handling of option unwrapping
• Extracted resolve_chain_spec_paths() to isolate complex path resolution logic based on command context and namespace capabilities
• Extracted prepare_raw_spec_command() to handle command preparation including template replacement and --raw flag addition
• Extracted parse_command_string() to separate string parsing concerns
• Extracted execute_generate_command() to handle local vs remote command execution
• Extracted finalize_raw_spec() to handle post-generation processing

The refactored build_raw_with_command now reads as a clear sequence of high-level steps, making the function's intent and flow much easier to understand. All helper methods are single-responsibility and testable.

Behavior is unchanged - this is a pure refactoring for clarity.

[cla-bot-2021]

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