Improves branch deletion by avoiding the use of the terminal

[eamodio]

Refs: #3528

Overview

Replaces the terminal-based branch deletion approach with direct Git API calls that provide better error handling and user experience.

Key Improvements

Enhanced Error Handling

• Adds specific error types and reasons for branch operations including already exists, not fully merged, invalid names, and missing remote references
• Provides contextual error messages that help users understand what went wrong and why

Better User Experience

• Shows confirmation dialog when attempting to delete unmerged branches, allowing users to force delete if desired
• Handles both local and remote branch deletions through the same interface
• Processes multiple branch deletions individually to avoid failing entire operations due to single branch issues

API Consistency

• Standardizes error handling patterns across branch and tag operations
• Adds dedicated methods for local and remote branch deletion that mirror existing tag operations
• Improves logging by including operation context in error messages

Technical Changes

• Introduces BranchError class with specific error reasons for different failure scenarios
• Adds deleteLocalBranch and deleteRemoteBranch methods to the branches sub-provider
• Updates push operations to handle remote reference deletion errors
• Refactors branch deletion logic to iterate through references individually rather than batch processing

[axosoft-ramint]

LGTM, works fine