[sancov] Switch to OptTable from llvm::cl

Switch the parse of command line options from llvm::cl to OptTable.

The motivation for this change is to continue adding llvm based tools
to the llvm driver multicall. For more information about the proposal
and motivation, please see https://discourse.llvm.org/t/rfc-llvm-busybox-proposal/58494

Reviewed By: leonardchan

Differential Revision: https://reviews.llvm.org/D155119