Unitfy API of get_modules
    
    Originally, there are two API to query module builds from MBS, get_modules and
    get_modules_with_requires. This patch refactors and unify the API to a single
    method get_modules with two addiitonal optional arguments requires and
    buildrequires. As a result, to get module builds with requires or buildrequires
    or both, no need to write if-else in the old way.
    
    Signed-off-by: Chenxiong Qi <cqi@redhat.com>