Update .vimrc with new plugin configurations

[pallavJha]

This pull request makes significant updates to the .vimrc configuration, focusing on modernizing plugin management, updating the user interface, and cleaning up legacy or redundant settings. The changes introduce vim-plug as the plugin manager, add several popular plugins, update color scheme settings, and remove a large amount of old or unused configuration, making the setup more streamlined and maintainable.

Plugin management and additions:

• Replaces pathogen with vim-plug for plugin management, and adds plugins like NERDTree, vim-airline, vim-airline-themes, and fzf.vim to enhance file navigation and the status/tab line (.vimrc).
• Adds configuration for fzf.vim, including a key mapping (<C-p>) to quickly open the file finder and sets up the runtime path for macOS users (.vimrc).

User interface and appearance:

• Updates color scheme settings: switches to the retrobox colorscheme, enables 256 colors, and adjusts related settings for better appearance and compatibility (.vimrc).
• Moves the status line configuration and related settings, including displaying the full file path, to a more prominent place in the config (.vimrc).

Configuration cleanup and simplification:

• Removes large sections of legacy or plugin-specific configuration (e.g., for ctrlp.vim, vim-lsc, tabline, and code formatting), as well as some default mappings and status line customizations, to reduce clutter and potential conflicts (.vimrc).
• Comments out some wrapping and column settings, making them easier to re-enable if needed, and adds a new autocommand for Markdown filetype detection (.vimrc) [1] [2].Refactor .vimrc to improve plugin management and settings.