improve handling of wire -> bus

[Thomas Pointhuber]

## Feature Request

Currently, it is easy to do bus -> wire using "unfold from bus", which automatically creates the bus connection and the continuing wire with the correct label attached.

I would like to propose to have this ability for the reverse direction as well: When a user places a wire where the end-point touches a bus, a "bus input" element is displayed, and when finishing the action, a menu appears where the user can select the bus entry. This could also be implemented for "bus -> wire", so users do not need to enter the context menu to start the connection. This should vastly improve the workflow because users can connect wire -> bus without changing between multiple tools (place wire, place bus input, place and set label).

When this is done, the "bus input" element would no longer be required to be manually placed by a user and could be removed from the toolbar as well.

## Version Information

Application: eeschema
Version: (5.1.0-541-g5c3952114), debug build
Libraries:
    wxWidgets 3.0.4
    libcurl/7.64.1 OpenSSL/1.1.1b zlib/1.2.11 libidn2/2.1.1 libpsl/0.20.2 (+libidn2/2.1.1) libssh2/1.8.1 nghttp2/1.36.0
Platform: Linux 5.0.7-arch1-1-ARCH x86_64, 64 bit, Little endian, wxGTK
Build Info:
    wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8) GTK+ 3.24
    Boost: 1.69.0
    OpenCASCADE Community Edition: 6.9.1
    Curl: 7.64.1
    Compiler: Clang 8.0.0 with C++ ABI 1002

Build settings:
    USE_WX_GRAPHICS_CONTEXT=OFF
    USE_WX_OVERLAY=ON
    KICAD_SCRIPTING=ON
    KICAD_SCRIPTING_MODULES=ON
    KICAD_SCRIPTING_PYTHON3=ON
    KICAD_SCRIPTING_WXPYTHON=ON
    KICAD_SCRIPTING_WXPYTHON_PHOENIX=ON
    KICAD_SCRIPTING_ACTION_MENU=ON
    BUILD_GITHUB_PLUGIN=ON
    KICAD_USE_OCE=ON
    KICAD_USE_OCC=OFF
    KICAD_SPICE=ON

[KiCad Janitor (kicad-janitor)]

KiCad bug tracker has moved to Gitlab. This report is now available here: https://gitlab.com/kicad/code/kicad/-/issues/2419