[clang-tidy][NFC] Remove ModernizeTidyModule::getModuleOptions

[clang-tidy][NFC] Remove ModernizeTidyModule::getModuleOptions

Most of the options stated there are duplicated already in
the implementation of each check as a default value for
each option.

The only place where this is not the case is the nullptr
check. Move the default option there instead. Only the
HICPP guidelines alias this modernize check, and there is
nothing in the documentation that suggests it should have
a different default value than the main modernize check.

Differential Revision: https://reviews.llvm.org/D143843