optimize annular rings for unconnected inner layers

[Thomas Pointhuber]

Related forum post: https://forum.kicad.info/t/optimizing-annular-rings-of-vias-in-inner-layers/1514

When you have a multilayer board, you can set a pad to have copper either on top, bottom, or all layers. In fact, this means the pad requires in the inner layers as much space as on the outer layer. Especially when the pad is unconnected, having the possibility to reduce the annular ring width would be highly beneficial.

# Version Information

Application: kicad
Version: (6.0.0-rc1-dev-373-g32d262b0f), debug build
Libraries:
    wxWidgets 3.1.1
    libcurl/7.61.0 OpenSSL/1.1.0i zlib/1.2.11 libidn2/2.0.5 libpsl/0.20.2 (+libidn2/2.0.4) nghttp2/1.32.0
Platform: Linux 4.18.3-arch1-1-ARCH x86_64, 64 bit, Little endian, wxGTK
Build Info:
    wxWidgets: 3.1.1 (wchar_t,wx containers) GTK+ 2.24
    Boost: 1.67.0
    OpenCASCADE Community Edition: 6.9.1
    Curl: 7.61.0
    Compiler: Clang 6.0.1 with C++ ABI 1002

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

[RyanFav (rerouter)]

To Add to this, It is Industry fab practice to remove unused via pads on internal layers,

This was discussed on the forum 3 years ago, I am linking it for reference to the devs.

https://forum.kicad.info/t/optimizing-annular-rings-of-vias-in-inner-layers/1514/13