Use new Gaudi CMake style configuration

now that the nightly builds can transparently build projects using the new configuration style of Gaudi (basically standard CMake projects), we can clean Detector from all the related hacks.

To do:

• drop FindGitCondDB.cmake (requires %0.1.2 in GitCondDB)
• fix implementation of run script (it might be possible to use the toolchain generated wrapper script, see https://gitlab.cern.ch/lhcb-core/lcg-toolchains/-/blob/b4722c43d58ffaf6d4aa495b90f77a679651ffd1/fragments/main.cmake#L70)
• remove unused bits from old-style configuration in cmake directory

Requires lhcb-core/LbDevTools!117 (merged)