feat: Implemented changedFilePattern && migrated raw Git cmds to go-git

[ChanduBobbili]

This pull request transitions the CLI's internal Git operations to use the go-git library and introduces the changedFilePattern feature to selectively track specific file modifications.

Key Changes:

• go-git Migration: Replaced brittle os/exec shell calls to the local Git binary with go-git, a pure Go implementation of Git, for tasks like reading tree states and checking diffs.
• changedFilePattern Implementation: Added logic to filter the list of changed files against user-defined patterns, allowing the CLI to ignore irrelevant modifications (like test files or documentation) when evaluating changesets.
• Refactored Git Utilities: Updated internal functions to interact natively with go-git repositories, worktrees, and object models instead of parsing raw stdout strings from CLI commands.
• Improved Error Handling: Leveraged go-git's typed errors to provide more reliable and actionable error messages during Git operations.

Motivation: Relying on os/exec to run Git commands is prone to cross-platform issues, formatting inconsistencies, and requires the host machine to have Git installed. Migrating to go-git makes the changesetgoo binary entirely self-contained, robust, and idiomatic to Go. Furthermore, adding changedFilePattern gives developers fine-grained control over the changeset generation process, ensuring that semantic versions are only bumped when relevant codebase files are altered.