Always use Gambit layout when loading from EFG

[edwardchalstrey1]

Requested enahancement or feature

• Update the logic in generate_tikz to use the gambit layout when receiving a EFG file, as is done when receiving a game object:

    # If user supplied an EFG file, convert it to .ef first so the existing
    # ef-based pipeline can be reused. efg_dl_ef returns a path string when
    # it successfully writes the .ef file.
    ef_file = game
    if isinstance(game, str):
        if game.lower().endswith('.efg'):
            try:
                ef_file = efg_dl_ef(game)
            except Exception:
                # fall through and let ef_to_tex raise a clearer error later
                pass
    else:
        from .gambit_layout import gambit_layout_to_ef
        # Generate the ef, use normalised spacing options
        ef_file = gambit_layout_to_ef(
            game,
            save_to=save_to,
            level_multiplier=level_scaling*4,
            sublevel_multiplier=sublevel_scaling*2 ,
            xshift_multiplier=width_scaling*2,
            hide_action_labels=hide_action_labels,
            shared_terminal_depth=shared_terminal_depth,
        )

• Remove the efg_dl_ef function and DefaultLayout which are no longer required.