Trigger/TrigTools/TrigMuon*: Move interfaces and cmake cleanup
Move the two interfaces ITrigMuonBackExtrapolator
and ITrigMuonRoITool
from their "implementation packages" to TrigMuonToolInterfaces. This allows TrigMuonBackExtrapolator and TrigMuonRoITools to become component-only packages.
Also cleanup cmake configuration and enable flake8 where applicable.