feat: implement interactive_custom_command for mid-execution user prompts

[KarolinaPomian]

This pull request introduces support for interactive command execution in InteractiveSSHConnection, enabling tools like EEUpdate that pause mid-output and require user input to complete without hanging.

Interactive command handling:

Added a new interactive_custom_command method to InteractiveSSHConnection that executes commands requiring mid-execution user prompts. Unlike execute_command, which only waits for the shell prompt to return, this method polls the channel in a loop and automatically responds to two interactive patterns:

"Press to continue..." — sends a newline when press_enter=True, allowing paged help output (e.g. eeupdate -h) to scroll through all pages
"Continue (Y or N)?" — sends the provided confirm character (e.g. "y" or "n") when set, enabling destructive commands like -nvm_clear to proceed without hanging
The method returns a ConnectionCompletedProcess with both stdout and raw_output set to the full collected output, and return_code retrieved via the existing _get_return_code mechanism.

Base class declaration:

Added interactive_custom_command to the Connection base class in base.py as a non-abstract method raising NotImplementedError, so connection types that do not implement it (SSH, WinRM, RPyC, etc.) produce a clear, descriptive error instead of a silent AttributeError.

Documentation updates:

README.md — Added interactive_custom_command to the InteractiveSSHConnection Public APIs section, documenting the press_enter and confirm parameters and the return type
CHANGELOG.md — Added an Unreleased entry describing the new feature