SPI-2548: Add 105b_LHCB toolchains

To run the testing, add a comment with:

Bot test PACKAGE[ PACKAGE2 ...]|all in TOOLCHAIN|all [(only|also) for ARCH-LABEL-COMPILER-BUILDTYPE] please!

later followed by

Bot repeat please!

To ensure patches required for existing LCG branches are not lost, please add the respective labels: alsoTargeting:LCG_102-patches, alsoTargeting:master, etc.

cmake/toolchain/heptools-105b_LHCB_7.cmake

+#---List of externals----------------------------------------------
+set(LCG_PYTHON_VERSION 3)
+include(heptools-105b)
+
+SET(LHCB_JSON_FILE https://gitlab.cern.ch/lhcb-core/rpm-recipes/-/raw/master/LHCBEXTERNALS/105/LHCBEXTERNALS_105b_LHCB_7.json)
+
+include(heptools-lhcbsetup)